Evidence used
- No CISA KEV confirmation is currently recorded.
- A structured source references public exploit or proof-of-concept material.
- EPSS is 6.12% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-25217High confidence
A buffer overrun in lease file parsing code can be used to exploit a common vulnerability shared by dhcpd and dhclient
ISC · ISC DHCP
7.4HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 13 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict local access and enforce least privilege on affected hosts.
- Increase monitoring for the attack path and post-exploitation behaviour described in the report.
Verification
- Confirm that the asset runs ISC ISC DHCP and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 13 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- SICK PSIRT: 1 affected or under-investigation product state without a fixed product state in the same current advisory
- SICK PSIRT: 1 affected or under-investigation product state without a fixed product state in the same current advisory
- Siemens ProductCERT: 1 affected or under-investigation product state without a fixed product state in the same current advisory
- Siemens ProductCERT: 10 affected or under-investigation product states without a fixed product state in the same current advisory
Distribution package intelligence
2 package statesRelease-specific package status
Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | isc-dhcp | Vendor fix publishedDebian records a fixed source-package version for this release. | 4.4.1-2.3 | Debian Security Tracker ↗Source updated 23 Oct 2026 |
| Debian bookwormbookworm · source | isc-dhcp | Vendor fix publishedDebian records a fixed source-package version for this release. | 4.4.1-2.3 | Debian Security Tracker ↗Source updated 23 Oct 2026 |
Direct vendor intelligence
5 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2021-25217 · CSAF 2.0 · revision 58 · interimSUSE Product Security TeamCVE-2021-25217
The vendor explicitly identifies these products as affected by this CVE.
- dhcp as component of SUSE Linux Enterprise Server for SAP Applications 12 SP5
- SLES 15 SP1 CHOST Images for Amazon EC2
- SLES 15 SP4 CHOST Images for Amazon EC2
- SLES 15 SP5 CHOST Images for Amazon EC2
- SLES 15 SP1 CHOST Images for Google
- SLES 15 SP2 CHOST Images for Google
- SLES 15 SP3 CHOST Images for Google
- SLES 15 SP4 CHOST Images for Google
- SLES 15 SP5 CHOST Images for Google
- SLES 15 SP1 CHOST Images for Microsoft Azure
- SLES 15 SP2 CHOST Images for Microsoft Azure
- SLES 15 SP4 CHOST Images for Microsoft Azure
- Summary
- In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.
- Remediation
- To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
SCA-2025-0011 · CSAF 2.0 · revision 1.0.0 · finalSICK PSIRTVulnerabilities affecting Endress+Hauser SSG-E210GC
The vendor explicitly identifies these products as affected by this CVE.
- Endress+Hauser SSG-E210GC all Firmware versions
- Summary
- In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.
- Remediation
- Please make sure that only trusted entities have access to the device. Furthermore, you should apply the following General Security Measures when operating the product to mitigate the associated security risk. The collected resources "SICK Operating Guidelines" and "ICS-CERT recommended practices on Industrial Security" could help to implement the general security practices.
SCA-2025-0009 · CSAF 2.0 · revision 1 · finalSICK PSIRTVulnerabilities affecting SICK TDC-E210GC
The vendor explicitly identifies these products as affected by this CVE.
- SICK TDC-E210GC all Firmware versions
- Summary
- In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.
- Remediation
- Please make sure that only trusted entities have access to the device. Furthermore, you should apply the following General Security Measures when operating the product to mitigate the associated security risk. The collected resources "SICK Operating Guidelines" and "ICS-CERT recommended practices on Industrial Security" could help to implement the general security practices.
SSA-637483 · CSAF 2.0 · revision 1 · finalSiemens ProductCERTSSA-637483 Third-Party Component Vulnerabilities in SINEC INS before V1.0 SP2
The vendor explicitly identifies these products as affected by this CVE.
- SINEC INS
- Summary
- The affected products contain the third party component, ISC DHCP, that possesses a vulnerability if used as a DHCP client or server. The vulnerability affects the DHCP package when storing and reading DHCP lease information containing particular option information. An attacker could exploit this vulnerability to affect the availability of the DHCP client or server, or in the worst case affect the confidentiality or integrity of device through a buffer overflow or cause a remote-code execution.
- Remediation
- Update to V1.0 SP2 or later version
SSA-406691 · CSAF 2.0 · revision 1 · finalSiemens ProductCERTSSA-406691: Buffer Vulnerabilities in DHCP function of RUGGEDCOM ROX products
The vendor explicitly identifies these products as affected by this CVE.
- RUGGEDCOM ROX MX5000
- RUGGEDCOM ROX RX1400
- RUGGEDCOM ROX RX1500
- RUGGEDCOM ROX RX1501
- RUGGEDCOM ROX RX1510
- RUGGEDCOM ROX RX1511
- RUGGEDCOM ROX RX1512
- RUGGEDCOM ROX RX1524
- RUGGEDCOM ROX RX1536
- RUGGEDCOM ROX RX5000
- Summary
- The affected products contain the third party component, ISC DHCP, that possesses a vulnerability if used as a DHCP client or server. The vulnerability affects the DHCP package when storing and reading DHCP lease information containing particular option information. An attacker could exploit this vulnerability to affect the availability of the DHCP client or server, or in the worst case affect the confidentiality or integrity of device through a buffer overflow or cause a remote-code execution.
- Remediation
- Update to V2.15.0 or later version
High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 13 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.
What
In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.
Why
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
How
An attacker operating through an adjacent network may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.
What
In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.
Why
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
How
An attacker operating through an adjacent network may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material Reference recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.
- Likely attack path
- an adjacent network → Improper Restriction of Operations within the Bounds of a Memory Buffer → disrupt the affected service
- Attack surface
- Adjacent
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Changed: exploitation can affect a different security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-119 ↗
CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVAdjacentAttack vector: The attacker must be on an adjacent or logically close network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Affected
- dhcp as component of SUSE Linux Enterprise Server for SAP Applications 12 SP5
- SLES 15 SP1 CHOST Images for Amazon EC2
- SLES 15 SP4 CHOST Images for Amazon EC2
- SLES 15 SP5 CHOST Images for Amazon EC2
- SLES 15 SP1 CHOST Images for Google
- SLES 15 SP2 CHOST Images for Google
- SLES 15 SP3 CHOST Images for Google
- SLES 15 SP4 CHOST Images for Google
- SLES 15 SP5 CHOST Images for Google
- SLES 15 SP1 CHOST Images for Microsoft Azure
- SLES 15 SP2 CHOST Images for Microsoft Azure
- SLES 15 SP4 CHOST Images for Microsoft Azure
- SLES 15 SP5 CHOST Images for Microsoft Azure
- Fixed
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 26 May 2021 · Last source change 16 Sept 2024, 22:08 UTC · CWE-119 · Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2021-12128
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceNIST NVD
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: sick.com/sca-2025-0011.json; removed remediation: endress.com.SICK PSIRT ↗
- Before
- remediation: endress.com
- After
- remediation: sick.com/sca-2025-0011.json
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: sick.com/special_information_sick_operating_guidelines_cybersecurity_by_sick_en_im0106719.pdf; removed remediation: sick.com/psirt.SICK PSIRT ↗
- Before
- remediation: sick.com/psirt
- After
- remediation: sick.com/special_information_sick_operating_guidelines_cybersecurity_by_sick_en_im0106719.pdf
- Affected versionsThe structured affected or fixed version information changed.Siemens ProductCERT ↗
- Before
- 4.1 ESV < 4.1-ESV-R16-P1; 4.4 < 4.4.2-P1 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
- After
- 4.1 ESV < 4.1-ESV-R16-P1; 4.4 < 4.4.2-P1 · Fixed: Update to V2.15.0 or later version
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.