Linux: Out-of-bounds Read
CVE-2025-39943 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 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 773fddf976d282ef059c36c575ddb81567acd6bc, bdaab5c6538e250a9654127e688ecbbeb6f771d5, eb0378dde086363046ed3d7db7f126fc3f76fd70 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 0.26% 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 773fddf976d282ef059c36c575ddb81567acd6bc or bdaab5c6538e250a9654127e688ecbbeb6f771d5 or eb0378dde086363046ed3d7db7f126fc3f76fd70 or 8be498fcbd5b07272f560b45981d4b9e5a2ad885, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.194 or 6.1.154 or 6.6.108 or 6.12.49, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 2ea086e35c3d726a3bacd0a971c1f02a50e98206 up to, but not including, 773fddf976d282ef059c36c575ddb81567acd6bc; 2ea086e35c3d726a3bacd0a971c1f02a50e98206 up to, but not including, bdaab5c6538e250a9654127e688ecbbeb6f771d5; 2ea086e35c3d726a3bacd0a971c1f02a50e98206 up to, but not including, eb0378dde086363046ed3d7db7f126fc3f76fd70; 2ea086e35c3d726a3bacd0a971c1f02a50e98206 up to, but not including, 8be498fcbd5b07272f560b45981d4b9e5a2ad885; 2ea086e35c3d726a3bacd0a971c1f02a50e98206 up to, but not including, 529b121b00a6ee3c88fb3c01b443b2b81f686d48; 2ea086e35c3d726a3bacd0a971c1f02a50e98206 up to, but not including, 5282491fc49d5614ac6ddcd012e5743eecb6a67c; 5.15 | 773fddf976d282ef059c36c575ddb81567acd6bc, bdaab5c6538e250a9654127e688ecbbeb6f771d5, eb0378dde086363046ed3d7db7f126fc3f76fd70, 8be498fcbd5b07272f560b45981d4b9e5a2ad885, 529b121b00a6ee3c88fb3c01b443b2b81f686d48, 5282491fc49d5614ac6ddcd012e5743eecb6a67c |
| Linux | Linux Kernel | 5.15.1 up to, but not including, 5.15.194; 5.16 up to, but not including, 6.1.154; 6.2 up to, but not including, 6.6.108; 6.7 up to, but not including, 6.12.49; 6.13 up to, but not including, 6.16.9; 5.15; 6.17 | 5.15.194, 6.1.154, 6.6.108, 6.12.49, 6.16.9 |
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
- NoneNothing can be modified.
- 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:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.4 | Critical | CNA |
| CVSS 3.1 | 7.1 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: smbdirect: validate data_offset and data_length field of smb_direct_data_transfer If data_offset and data_length of smb_direct_data_transfer struct are invalid, out of bounds issue could happen. This patch validate data_offset and data_length field in recv_done.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/5282491fc49d5614ac6ddcd012e5743eecb6a67c
- git.kernel.org/stable/c/529b121b00a6ee3c88fb3c01b443b2b81f686d48
- git.kernel.org/stable/c/773fddf976d282ef059c36c575ddb81567acd6bc
- git.kernel.org/stable/c/8be498fcbd5b07272f560b45981d4b9e5a2ad885
- git.kernel.org/stable/c/bdaab5c6538e250a9654127e688ecbbeb6f771d5
- git.kernel.org/stable/c/eb0378dde086363046ed3d7db7f126fc3f76fd70
Recent Out-of-bounds Read vulnerabilities
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
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