CVE-2025-21840

CVE-2025-21840 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

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 ]

Frequently asked questions

What is CVE-2025-21840?
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 ]
How severe is CVE-2025-21840?
CVE-2025-21840 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-21840 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21840?
CVE-2025-21840 primarily affects Linux Linux Kernel. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21840?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-21840 have an EU (EUVD) identifier?
Yes. CVE-2025-21840 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-7591.
When was CVE-2025-21840 published?
CVE-2025-21840 was published on 2025-03-07 and last updated on 2026-06-17.

References

Affected products (3)

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