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CVE Record

CVE-2025-21840: thermal/netlink: Prevent userspace segmentation fault by adjusting UAPI header

In the Linux kernel, the following vulnerability has been resolved: thermal/netlink: Prevent userspace segmentation fault by adjusting UAPI header The intel-lpmd tool [1], which uses the THERMAL_GENL_ATTR_CPU_CAPABILITY attribute to receive HFI events from kernel space, encounters a segmentation fault after commit 1773572863c4 ("thermal: netlink: Add the commands and the events for the thresholds"). The issue arises because the THERMAL_GENL_ATTR_CPU_CAPABILITY raw value was changed while intel_lpmd still uses the old value. Although intel_lpmd can be updated to check the THERMAL_GENL_VERSION and use the appropriate THERMAL_GENL_ATTR_CPU_CAPABILITY value, the commit itself is questionable. The commit introduced a new element in the middle of enum thermal_genl_attr, which affects many existing attributes and introduces potential risks and unnecessary maintenance burdens for userspace thermal netlink event users. Solve the issue by moving the newly introduced THERMAL_GENL_ATTR_TZ_PREV_TEMP attribute to the end of the enum thermal_genl_attr. This ensures that all existing thermal generic netlink attributes remain unaffected. [ rjw: Subject edits ]

UnknownCVSS not scoredNot KEV-listedUpdated
Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can crash userspace thermal-management software because a kernel interface value changed unexpectedly. The cited example is intel-lpmd receiving thermal/HFI events. Sources describe a reliability and compatibility problem, not data theft or remote compromise.

Executive priority

Treat this as a low-priority reliability fix unless your fleet depends on Linux thermal management tooling. Include it in normal kernel patch cycles, with faster attention for laptops, edge systems, or performance-managed hosts using intel-lpmd.

Technical view

A thermal generic netlink UAPI enum was changed by inserting THERMAL_GENL_ATTR_TZ_PREV_TEMP in the middle. Existing attribute numbers shifted, so userspace expecting the old THERMAL_GENL_ATTR_CPU_CAPABILITY value could misinterpret events and segfault. The fix moves the new attribute to the end.

Likely exposure

Exposure appears limited to Linux systems on affected 6.13-era kernels that use thermal generic netlink consumers, especially intel-lpmd/HFI event handling. Systems not using these userspace thermal event paths are less likely to see impact.

Exploitation context

The source bundle does not cite active exploitation, KEV listing, public exploit activity, or remote attack paths. The documented symptom is a userspace segmentation fault triggered by kernel/userspace API incompatibility after a kernel change.

Researcher notes

The evidence supports an ABI compatibility regression in Linux thermal netlink attributes. The CVE record lists no CVSS, CWE, or KEV status. Avoid broad claims beyond userspace crash risk unless vendor advisories add more impact detail.

Mitigation direction

  • Apply a vendor kernel update containing the referenced stable thermal/netlink fix.
  • Prioritize systems using intel-lpmd or thermal generic netlink event consumers.
  • Check distribution advisories before relying on upstream commit hashes alone.
  • If patching is delayed, review operational impact of affected thermal userspace tooling.

Validation and detection

  • Inventory systems running affected Linux 6.13 or 6.14 kernel builds.
  • Confirm whether the stable fix is present in the deployed kernel package.
  • Identify hosts running intel-lpmd or other thermal generic netlink consumers.
  • Review crash reports for intel-lpmd segmentation faults after kernel updates.
  • After patching, verify thermal event consumers remain stable under normal workload.
Prepared
Confidence
high
Sources
4

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

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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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
3Timeline events
0ADP providers
3Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1773572863c43a14a3e45f0591f28b7dec1ee52a, 1773572863c43a14a3e45f0591f28b7dec1ee52aunaffected
LinuxLinux6.13, 0, 6.13.4, 6.14affected
Weakness

CWE details

No CWE listed

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