Linux: Use After Free
CVE-2025-21967 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 ffe0909010b21df8f948d624ad00cf14dd856721, fb776765bfc21d5e4ed03bb3d4406c2b86ff1ac3, 62746ae3f5414244a96293e3b017be637b641280 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 0.38% 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 ffe0909010b21df8f948d624ad00cf14dd856721 or fb776765bfc21d5e4ed03bb3d4406c2b86ff1ac3 or 62746ae3f5414244a96293e3b017be637b641280 or eb51f6f59d19b92f6fe84d3873f958495ab32f0a, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.84 or 6.12.20 or 6.13.8, 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, ffe0909010b21df8f948d624ad00cf14dd856721; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, fb776765bfc21d5e4ed03bb3d4406c2b86ff1ac3; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 62746ae3f5414244a96293e3b017be637b641280; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, eb51f6f59d19b92f6fe84d3873f958495ab32f0a; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, bb39ed47065455604729404729d9116868638d31; 5.15 | ffe0909010b21df8f948d624ad00cf14dd856721, fb776765bfc21d5e4ed03bb3d4406c2b86ff1ac3, 62746ae3f5414244a96293e3b017be637b641280, eb51f6f59d19b92f6fe84d3873f958495ab32f0a, bb39ed47065455604729404729d9116868638d31 |
| Linux | Linux Kernel | 5.15 up to, but not including, 6.6.84; 6.7 up to, but not including, 6.12.20; 6.13 up to, but not including, 6.13.8; 6.14 | 6.6.84, 6.12.20, 6.13.8 |
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 ksmbd_free_work_struct ->interim_entry of ksmbd_work could be deleted after oplock is freed. We don't need to manage it with linked list. The interim request could be immediately sent whenever a oplock break wait is needed.
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
Other references
Recent Use After Free vulnerabilities
- 7.8 High 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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