Linux: Use After Free
CVE-2025-37778 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 b61f04d5d73c53d183019bafe22fb700a739bac5, d5b554bc8d554ed6ddf443d3db2fad9f665cec10, 1db2451de23e98bc864c6a6e52aa0d82c91cb325 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 1.16% chance of exploitation within 30 days, higher than 68% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to b61f04d5d73c53d183019bafe22fb700a739bac5 or d5b554bc8d554ed6ddf443d3db2fad9f665cec10 or 1db2451de23e98bc864c6a6e52aa0d82c91cb325 or 6e30c0e10210c714f3d4453dc258d4abcc70364e, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.135 or 6.6.88 or 6.12.25 or 6.14.4, 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, b61f04d5d73c53d183019bafe22fb700a739bac5; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, d5b554bc8d554ed6ddf443d3db2fad9f665cec10; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 1db2451de23e98bc864c6a6e52aa0d82c91cb325; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 6e30c0e10210c714f3d4453dc258d4abcc70364e; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, e83e39a5f6a01a81411a4558a59a10f87aa88dd6; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 1e440d5b25b7efccb3defe542a73c51005799a5f; 5.15 | b61f04d5d73c53d183019bafe22fb700a739bac5, d5b554bc8d554ed6ddf443d3db2fad9f665cec10, 1db2451de23e98bc864c6a6e52aa0d82c91cb325, 6e30c0e10210c714f3d4453dc258d4abcc70364e, e83e39a5f6a01a81411a4558a59a10f87aa88dd6, 1e440d5b25b7efccb3defe542a73c51005799a5f |
| Linux | Linux Kernel | 5.15 up to, but not including, 6.1.135; 6.2 up to, but not including, 6.6.88; 6.7 up to, but not including, 6.12.25; 6.13 up to, but not including, 6.14.4; 6.15 | 6.1.135, 6.6.88, 6.12.25, 6.14.4 |
| Debian | Debian Linux | 11.0 | Not stated |
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 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: Fix dangling pointer in krb_authenticate krb_authenticate frees sess->user and does not set the pointer to NULL. It calls ksmbd_krb5_authenticate to reinitialise sess->user but that function may return without doing so. If that happens then smb2_sess_setup, which calls krb_authenticate, will be accessing free'd memory when it later uses 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.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/1db2451de23e98bc864c6a6e52aa0d82c91cb325
- git.kernel.org/stable/c/1e440d5b25b7efccb3defe542a73c51005799a5f
- git.kernel.org/stable/c/6e30c0e10210c714f3d4453dc258d4abcc70364e
- git.kernel.org/stable/c/d5b554bc8d554ed6ddf443d3db2fad9f665cec10
- git.kernel.org/stable/c/e83e39a5f6a01a81411a4558a59a10f87aa88dd6
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/05/msg00045.htmlMailing List, 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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