Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 3.62% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-42377High confidence
busybox — Free of Memory not on the Heap
busybox · busybox
Official source article: Siemens SSA-831302 ↗. Check the applicable product and release in the original source.
9.8CriticalCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productCritical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 30 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 severityCritical→Operational priority:Critical, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs busybox busybox 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 30 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Siemens ProductCERT: 1 affected or under-investigation product state without a fixed product state in the same current advisory
- Siemens ProductCERT: 20 affected or under-investigation product states without a fixed product state in the same current advisory
- Siemens ProductCERT: 9 affected or under-investigation product states without a fixed product state in the same current advisory
Distribution package intelligence
7 package statesRelease-specific package status
Alpine, 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 |
|---|---|---|---|---|
| Alpine v3.23v3.23 · main | busybox | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 0 | Alpine Security Database ↗Source updated 3 Oct 2026 |
| Alpine v3.22v3.22 · main | busybox | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 0 | Alpine Security Database ↗Source updated 3 Oct 2026 |
| Alpine v3.21v3.21 · main | busybox | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 0 | Alpine Security Database ↗Source updated 3 Oct 2026 |
| Debian trixietrixie · source | busybox | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:1.35.0-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian bookwormbookworm · source | busybox | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:1.35.0-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian forkyforky · source | busybox | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:1.35.0-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian sidsid · source | busybox | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:1.35.0-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
Direct vendor intelligence
3 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.
SSA-831302 · CSAF 2.0 · revision 5 · interimSiemens ProductCERTSSA-831302: Vulnerabilities in the BIOS of the SIMATIC S7-1500 TM MFP before V1.3.0
The vendor explicitly identifies these products as affected by this CVE.
- SIMATIC S7-1500 TM MFP - BIOS
- Summary
- An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.
- Remediation
- Update to V1.3.0 or later version
SSA-419740 · CSAF 2.0 · revision 1 · finalSiemens ProductCERTSSA-419740: Multiple Third-Party Component Vulnerabilities in RUGGEDCOM and SCALANCE Products before V7.2
The vendor explicitly identifies these products as affected by this CVE.
- RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2)
- RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2)
- SCALANCE M804PB (6GK5804-0AP00-2AA2)
- SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2)
- SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2)
- SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2)
- SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2)
- SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2)
- SCALANCE M874-2 (6GK5874-2AA00-2AA2)
- SCALANCE M874-3 (6GK5874-3AA00-2AA2)
- SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2)
- SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2)
- Summary
- An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.
- Remediation
- Update to V7.2 or later version
SSA-565386 · CSAF 2.0 · revision 1 · interimSiemens ProductCERTSSA-565386: Third-Party Component Vulnerabilities in SCALANCE W-700 IEEE 802.11ax devices before V2.0
The vendor explicitly identifies these products as affected by this CVE.
- SCALANCE WAM763-1 (6GK5763-1AL00-7DA0)
- SCALANCE WAM766-1 (EU) (6GK5766-1GE00-7DA0)
- SCALANCE WAM766-1 (US) (6GK5766-1GE00-7DB0)
- SCALANCE WAM766-1 EEC (EU) (6GK5766-1GE00-7TA0)
- SCALANCE WAM766-1 EEC (US) (6GK5766-1GE00-7TB0)
- SCALANCE WUM763-1 (6GK5763-1AL00-3AA0)
- SCALANCE WUM763-1 (6GK5763-1AL00-3DA0)
- SCALANCE WUM766-1 (EU) (6GK5766-1GE00-3DA0)
- SCALANCE WUM766-1 (US) (6GK5766-1GE00-3DB0)
- Summary
- An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.
- Remediation
- Update to V2.0 or later version
Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 30 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
An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.
What
An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.
Why
The product calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
What
An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.
Why
The product calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
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 None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Free of Memory not on the Heap → execute code or commands in the affected security context
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-590 ↗
CWE-590: Free of Memory not on the Heap. The product calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a 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.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
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
- SIMATIC S7-1500 TM MFP - BIOS
- 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. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 15 Nov 2021 · Last source change 4 Aug 2024, 03:30 UTC · CWE-590 · Free of Memory not on the Heap
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
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-2021-29348
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceCNA
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
- Affected versionsThe structured affected or fixed version information changed.Siemens ProductCERT ↗
- Before
- unspecified < 1.34.0 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- unspecified < 1.34.0 · Fixed: Update to V1.3.0 or later version
- Remediation statusRemediation status changed from Awaiting fix to Patch available.Siemens ProductCERT ↗
- Before
- Awaiting fix
- After
- Patch available
CVE published
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.