Linux: Use After Free
CVE-2025-21945 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 410ce35a2ed6d0e114132bba29af49b69880c8c7, 8573571060ca466cbef2c6f03306b2cc7b883506, a0609097fd10d618aed4864038393dd75131289e 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 0.53% 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 410ce35a2ed6d0e114132bba29af49b69880c8c7 or 8573571060ca466cbef2c6f03306b2cc7b883506 or a0609097fd10d618aed4864038393dd75131289e or 636e021646cf9b52ddfea7c809b018e91f2188cb, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.131 or 6.6.83 or 6.12.19 or 6.13.7, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 410ce35a2ed6d0e114132bba29af49b69880c8c7; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 8573571060ca466cbef2c6f03306b2cc7b883506; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, a0609097fd10d618aed4864038393dd75131289e; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 636e021646cf9b52ddfea7c809b018e91f2188cb; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 84d2d1641b71dec326e8736a749b7ee76a9599fc; 5.15 | 410ce35a2ed6d0e114132bba29af49b69880c8c7, 8573571060ca466cbef2c6f03306b2cc7b883506, a0609097fd10d618aed4864038393dd75131289e, 636e021646cf9b52ddfea7c809b018e91f2188cb, 84d2d1641b71dec326e8736a749b7ee76a9599fc |
| Linux | Linux Kernel | 5.15 up to, but not including, 6.1.131; 6.2 up to, but not including, 6.6.83; 6.7 up to, but not including, 6.12.19; 6.13 up to, but not including, 6.13.7; 6.14 | 6.1.131, 6.6.83, 6.12.19, 6.13.7 |
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.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in smb2_lock If smb_lock->zero_len has value, ->llist of smb_lock is not delete and flock is old one. It will cause use-after-free on error handling routine.
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.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/410ce35a2ed6d0e114132bba29af49b69880c8c7
- git.kernel.org/stable/c/636e021646cf9b52ddfea7c809b018e91f2188cb
- git.kernel.org/stable/c/84d2d1641b71dec326e8736a749b7ee76a9599fc
- git.kernel.org/stable/c/8573571060ca466cbef2c6f03306b2cc7b883506
- git.kernel.org/stable/c/a0609097fd10d618aed4864038393dd75131289e
Other references
Recent Use After Free vulnerabilities
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