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CVE Record

CVE-2021-35039: kernel/module.c in the Linux kernel before 5.12.14 mishandles Signature Verification, aka CID-0c18f29aae7c.

kernel/module.c in the Linux kernel before 5.12.14 mishandles Signature Verification, aka CID-0c18f29aae7c. Without CONFIG_MODULE_SIG, verification that a kernel module is signed, for loading via init_module, does not occur for a module.sig_enforce=1 command-line argument.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can undermine a security expectation: systems booted with module.sig_enforce=1 may still load unsigned kernel modules if the kernel was built without CONFIG_MODULE_SIG. That matters only where administrators rely on signed-module enforcement to prevent untrusted kernel code.

Executive priority

Treat this as a targeted hardening gap, not a broad remote-compromise emergency. Prioritize regulated, appliance, or hardened Linux systems that depend on kernel module signing for trust boundaries.

Technical view

In Linux kernel module loading before 5.12.14, kernel/module.c did not enforce signature checks for init_module when CONFIG_MODULE_SIG was absent, even if module.sig_enforce=1 was supplied. The upstream fix is commit 0c18f29aae7c, referenced in the 5.12.14 changelog.

Likely exposure

Exposure is limited to Linux systems before the fixed kernel or vendor backport, built without CONFIG_MODULE_SIG, while relying on module.sig_enforce=1 for module-signature policy. Downstream affected versions are not fully enumerated in the bundle.

Exploitation context

The bundle does not show KEV listing or active exploitation. Practical abuse would require a path to load kernel modules, typically a highly privileged local capability, so this is mainly a defense-bypass concern for hardened Linux environments.

Researcher notes

Key uncertainty is downstream scope: the CVE bundle names upstream Linux before 5.12.14 and includes Debian and NetApp references, but does not provide a complete affected-product matrix, CVSS score, or exploitation evidence.

Mitigation direction

  • Update to Linux 5.12.14 or a vendor kernel containing the upstream fix.
  • Apply relevant distribution or appliance security updates from trusted vendor channels.
  • Use CONFIG_MODULE_SIG where signed-module enforcement is required.
  • Review boot configuration relying on module.sig_enforce=1 for false assurance.
  • Restrict module-loading privileges to trusted administrative paths only.

Validation and detection

  • Inventory Linux kernel versions and vendor patch levels across affected fleets.
  • Confirm whether kernels are built with CONFIG_MODULE_SIG enabled.
  • Check whether module.sig_enforce=1 is used in boot parameters.
  • Verify vendor advisories for backported fixes on maintained distributions.
  • Prioritize systems using signed modules as a security control.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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