Linux: Use After Free
CVE-2026-31652 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 447f8870b484f6596d7a7130e72bd0a3f1e037bb, 16c92e9bf55fa049ddb5e894dc0623dacd46a620, 4c04c6b47c361612b1d70cec8f7a60b1482d1400 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.11% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 447f8870b484f6596d7a7130e72bd0a3f1e037bb or 16c92e9bf55fa049ddb5e894dc0623dacd46a620 or 4c04c6b47c361612b1d70cec8f7a60b1482d1400, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.23 or 6.19.13, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 405f61996d9d2e9d497cd9f6b66f41dc28d3d1d8 up to, but not including, 447f8870b484f6596d7a7130e72bd0a3f1e037bb; 405f61996d9d2e9d497cd9f6b66f41dc28d3d1d8 up to, but not including, 16c92e9bf55fa049ddb5e894dc0623dacd46a620; 405f61996d9d2e9d497cd9f6b66f41dc28d3d1d8 up to, but not including, 4c04c6b47c361612b1d70cec8f7a60b1482d1400; 6.17 | 447f8870b484f6596d7a7130e72bd0a3f1e037bb, 16c92e9bf55fa049ddb5e894dc0623dacd46a620, 4c04c6b47c361612b1d70cec8f7a60b1482d1400 |
| Linux | Linux Kernel | 6.17.1 up to, but not including, 6.18.23; 6.19 up to, but not including, 6.19.13; 6.17; 7.0 | 6.18.23, 6.19.13 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
Official description
In the Linux kernel, the following vulnerability has been resolved: mm/damon/stat: deallocate damon_call() failure leaking damon_ctx damon_stat_start() always allocates the module's damon_ctx object (damon_stat_context). Meanwhile, if damon_call() in the function fails, the damon_ctx object is not deallocated. Hence, if the damon_call() is failed, and the user writes Y to “enabled” again, the previously allocated damon_ctx object is leaked. This cannot simply be fixed by deallocating the damon_ctx object when damon_call() fails. That's because damon_call() failure doesn't guarantee the kdamond main function, which accesses the damon_ctx object, is completely finished. In other words, if damon_stat_start() deallocates the damon_ctx object after damon_call() failure, the not-yet-terminated kdamond could access the freed memory (use-after-free). Fix the leak while avoiding the use-after-free by keeping returning damon_stat_start() without deallocating the damon_ctx object after damon_call() failure, but deallocating it when the function is invoked again and the kdamond is completely terminated. If the kdamond is not yet terminated, simply return -EAGAIN, as the kdamond will soon be terminated. The issue was discovered [1] by sashiko.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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