Evidence used
- No CISA KEV confirmation is currently recorded.
- Exploitation requires an existing local or physical foothold with privileges.
- EPSS is 0.43% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-42376High confidence
A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character
busybox · busybox
Official source article: Siemens SSA-831302 ↗. Check the applicable product and release in the original source.
5.5MediumCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. 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 severityMedium→Operational priority:Low, lowered one band.downgradedsince 4 Aug 2024
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict local access and enforce least privilege on affected hosts.
- 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
- A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very 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
- A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very 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
- A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very rare conditions of filtered command input.
- Remediation
- Update to V2.0 or later version
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. 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
A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very rare conditions of filtered command input.
What
A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very rare conditions of filtered command input.
Why
The product dereferences a pointer that it expects to be valid but is NULL.
How
An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.
What
A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very rare conditions of filtered command input.
Why
The product dereferences a pointer that it expects to be valid but is NULL.
How
An attacker operating through local access may attempt exploitation with low privileges. 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 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
- local access → NULL Pointer Dereference → disrupt the affected service
- Attack surface
- Local
- Privileges required
- Low: a basic authenticated account is required
- 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-476 ↗
CWE-476: NULL Pointer Dereference. The product dereferences a pointer that it expects to be valid but is NULL.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's 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
- The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
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. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 15 Nov 2021 · Last source change 4 Aug 2024, 03:30 UTC · CWE-476 · NULL Pointer Dereference
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-2021-29347
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.