CyberSecBulletin
CVE-2025-39689NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2025-39689 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 12064e1880fc9202be75ff668205b1703d92f74f, c4cd93811e038d19f961985735ef7bb128078dfb, e0b6b223167e1edde5c82edf38e393c06eda1f13 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 0.19% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 12064e1880fc9202be75ff668205b1703d92f74f or c4cd93811e038d19f961985735ef7bb128078dfb or e0b6b223167e1edde5c82edf38e393c06eda1f13 or a40c69f4f1ed96acbcd62e9b5ff3a596f0a91309, whichever matches your release line, or a later version.
  2. Update SIMATIC CN 4100 to V5.0 or a later version.
  3. Update Linux Kernel to 5.4.297 or 5.10.241 or 5.15.190 or 6.1.149, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxc20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, 12064e1880fc9202be75ff668205b1703d92f74f; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, c4cd93811e038d19f961985735ef7bb128078dfb; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, e0b6b223167e1edde5c82edf38e393c06eda1f13; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, a40c69f4f1ed96acbcd62e9b5ff3a596f0a91309; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, 3b114a3282ab1a12cb4618a8f45db5d7185e784a; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, c591ba1acd081d4980713e47869dd1cc3d963d19; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, 64db338140d2bad99a0a8c6a118dd60b3e1fb8cb; c20489dad156dd9919ebd854bbace46dbd2576a3 up to, but not including, bfb336cf97df7b37b2b2edec0f69773e06d11955; and 1 more ranges12064e1880fc9202be75ff668205b1703d92f74f, c4cd93811e038d19f961985735ef7bb128078dfb, e0b6b223167e1edde5c82edf38e393c06eda1f13, a40c69f4f1ed96acbcd62e9b5ff3a596f0a91309, 3b114a3282ab1a12cb4618a8f45db5d7185e784a, c591ba1acd081d4980713e47869dd1cc3d963d19
SiemensSIMATIC CN 4100before V5.0V5.0
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFPV3.1.5 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFPV3.1.5 and laterNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFPV3.1.5 and laterNot stated
LinuxLinux Kernel4.12 up to, but not including, 5.4.297; 5.5 up to, but not including, 5.10.241; 5.11 up to, but not including, 5.15.190; 5.16 up to, but not including, 6.1.149; 6.2 up to, but not including, 6.6.103; 6.7 up to, but not including, 6.12.44; 6.13 up to, but not including, 6.16.4; 6.175.4.297, 5.10.241, 5.15.190, 6.1.149, 6.6.103, 6.12.44
DebianDebian Linux11.0Not 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 systemScoreSeverityScored by
CVSS 3.17.8HighCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: ftrace: Also allocate and copy hash for reading of filter files Currently the reader of set_ftrace_filter and set_ftrace_notrace just adds the pointer to the global tracer hash to its iterator. Unlike the writer that allocates a copy of the hash, the reader keeps the pointer to the filter hashes. This is problematic because this pointer is static across function calls that release the locks that can update the global tracer hashes. This can cause UAF and similar bugs. Allocate and copy the hash for reading the filter files like it is done for the writers. This not only fixes UAF bugs, but also makes the code a bit simpler as it doesn't have to differentiate when to free the iterator's hash between writers and readers.

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.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Recent Use After Free vulnerabilities

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