Linux: Use After Free
CVE-2025-37899 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 931dc8a3670f71c45c0b1379ea4e92dafbda1aca, 70ad6455139e26e85f48f95d0e21f351c1909342, d5ec1d79509b3ee01de02c236f096bc050221b7f 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 0.88% chance of exploitation within 30 days, higher than 60% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 931dc8a3670f71c45c0b1379ea4e92dafbda1aca or 70ad6455139e26e85f48f95d0e21f351c1909342 or d5ec1d79509b3ee01de02c236f096bc050221b7f or 02d16046cd11a5c037b28c12ffb818c56dd3ef43, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.28 or 6.14.6, 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, 931dc8a3670f71c45c0b1379ea4e92dafbda1aca; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 70ad6455139e26e85f48f95d0e21f351c1909342; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, d5ec1d79509b3ee01de02c236f096bc050221b7f; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 02d16046cd11a5c037b28c12ffb818c56dd3ef43; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 2fc9feff45d92a92cd5f96487655d5be23fb7e2b; 5.15 | 931dc8a3670f71c45c0b1379ea4e92dafbda1aca, 70ad6455139e26e85f48f95d0e21f351c1909342, d5ec1d79509b3ee01de02c236f096bc050221b7f, 02d16046cd11a5c037b28c12ffb818c56dd3ef43, 2fc9feff45d92a92cd5f96487655d5be23fb7e2b |
| Linux | Linux Kernel | 5.15 up to, but not including, 6.12.28; 6.13 up to, but not including, 6.14.6; 6.15 | 6.12.28, 6.14.6 |
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 |
Official description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in session logoff The sess->user object can currently be in use by another thread, for example if another connection has sent a session setup request to bind to the session being free'd. The handler for that connection could be in the smb2_sess_setup function which makes use of sess->user.
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
Technical write-ups (may include proof of concept)
- news.ycombinator.com/item?id=44081338Exploit, Issue Tracking, Third Party Advisory
- sean.heelan.io/2025/05/22/how-i-used-o3-to-find-cve-2025-37899-a-remote-zeroday-vulnerability-in-the-linux-ke…Exploit, Third Party Advisory
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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