Evidence used
- No CISA KEV confirmation is currently recorded.
- Exploitation requires an existing local or physical foothold with privileges.
- EPSS is 0.31% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-33626High confidence
n/a — Inclusion of Functionality from Untrusted Control Sphere
Unknown · Unknown
Official source article: Siemens SSA-306654 ↗. Check the applicable product and release in the original source.
7.8HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 18 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:Medium, lowered one band.downgradedsince 11 Aug 2026
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 Unknown Unknown 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 18 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Siemens ProductCERT: 18 affected or under-investigation product states without a fixed product state in the same current advisory
Direct vendor intelligence
2 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-306654 · CSAF 2.0 · revision 11 · interimSiemens ProductCERTSSA-306654: Insyde BIOS Vulnerabilities in Siemens Industrial Products
The vendor explicitly identifies these products as affected by this CVE.
- RUGGEDCOM APE1808 - BIOS < V1.0.202N
- SIMATIC Field PG M5 < V22.01.10
- SIMATIC Field PG M6 < V26.01.13
- SIMATIC IPC127E < V27.01.09
- SIMATIC IPC227G < V28.01.04
- SIMATIC IPC277G < V28.01.04
- SIMATIC IPC277G PRO < V28.01.04
- SIMATIC IPC327G < V28.01.04
- SIMATIC IPC377G < V28.01.04
- SIMATIC IPC427E < V21.01.17
- SIMATIC IPC477E < V21.01.17
- SIMATIC IPC477E PRO < V21.01.17
- Summary
- In the kernel in Insyde InsydeH2O 5.x, certain SMM drivers did not correctly validate the CommBuffer and CommBufferSize parameters, allowing callers to corrupt either the firmware or the OS memory. The fixed versions for this issue in the PnpSmm, SmmResourceCheckDxe, and BeepStatusCode drivers are 05.08.23, 05.16.23, 05.26.23, 05.35.23, 05.43.23, and 05.51.23 (for Kernel 5.0 through 5.5).
- Remediation
- Update to V1.0.202N or later version
ARUBA-PSA-2022-002 · CSAF 2.0 · revision 2 · finalHPE Aruba NetworkingSMM Privilege Escalation Vulnerability
The vendor explicitly identifies these products as affected by this CVE.
- 9200 and 9000 Series Controllers and Gateways
- Summary
- A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated buffer pointer(QWORD values for CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.
- Remediation
- Upgrade to the fix version.
High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 18 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 vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated buffer pointer(QWORD values for CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.
What
A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated buffer pointer(QWORD values for CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.
Why
The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.
How
An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may execute code or commands in the affected security context.
What
A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated buffer pointer(QWORD values for CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.
Why
The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.
How
An attacker operating through local access may attempt exploitation with low privileges. 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
- local access → Inclusion of Functionality from Untrusted Control Sphere → execute code or commands in the affected security context
- 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-829 ↗
CWE-829: Inclusion of Functionality from Untrusted Control Sphere. The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.
- 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:H/I:H/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.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
- RUGGEDCOM APE1808 - BIOS < V1.0.202N
- SIMATIC Field PG M5 < V22.01.10
- SIMATIC Field PG M6 < V26.01.13
- SIMATIC IPC127E < V27.01.09
- SIMATIC IPC227G < V28.01.04
- SIMATIC IPC277G < V28.01.04
- SIMATIC IPC277G PRO < V28.01.04
- SIMATIC IPC327G < V28.01.04
- SIMATIC IPC377G < V28.01.04
- SIMATIC IPC427E < V21.01.17
- SIMATIC IPC477E < V21.01.17
- SIMATIC IPC477E PRO < V21.01.17
- SIMATIC IPC627E < V25.02.12
- SIMATIC IPC647E < V25.02.12
- SIMATIC IPC677E < V25.02.12
- SIMATIC IPC847E < V25.02.12
- SIMATIC ITP1000 < V23.01.10
- SIPLUS IPC427E < V21.01.17
- 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 1 Oct 2021 · Last source change 11 Aug 2026, 12:22 UTC · CWE-829 · Inclusion of Functionality from Untrusted Control Sphere
CVE recordCVE.org · 5.2
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-2021-20303
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceNIST NVD
NVD statusNVD modified after enrichment
Missing structured fields: affected product. Missing data is not evidence of low risk; review the primary advisory.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Siemens ProductCERT ↗
- Before
- n/a · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- n/a · Fixed: Update to V1.0.202N 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.