CyberSecBulletin
CVE-2025-38000NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2025-38000 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 1034e3310752e8675e313f7271b348914008719a, f9f593e34d2fb67644372c8f7b033bdc622ad228, 89c301e929a0db14ebd94b4d97764ce1d6981653 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 0.24% 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 1034e3310752e8675e313f7271b348914008719a or f9f593e34d2fb67644372c8f7b033bdc622ad228 or 89c301e929a0db14ebd94b4d97764ce1d6981653 or f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.4.294 or 5.10.238 or 5.15.185 or 6.1.141, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, 1034e3310752e8675e313f7271b348914008719a; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, f9f593e34d2fb67644372c8f7b033bdc622ad228; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, 89c301e929a0db14ebd94b4d97764ce1d6981653; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, 93c276942e75de0e5bc91576300d292e968f5a02; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, 49b21795b8e5654a7df3d910a12e1060da4c04cf; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, 3f3a22eebbc32b4fa8ce9c1d5f9db214b45b9335; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 up to, but not including, 3f981138109f63232a5fb7165938d4c945cc1b9d; and 1 more ranges1034e3310752e8675e313f7271b348914008719a, f9f593e34d2fb67644372c8f7b033bdc622ad228, 89c301e929a0db14ebd94b4d97764ce1d6981653, f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4, 93c276942e75de0e5bc91576300d292e968f5a02, 49b21795b8e5654a7df3d910a12e1060da4c04cf
LinuxLinux Kernel4.8 up to, but not including, 5.4.294; 5.5 up to, but not including, 5.10.238; 5.11 up to, but not including, 5.15.185; 5.16 up to, but not including, 6.1.141; 6.2 up to, but not including, 6.6.93; 6.7 up to, but not including, 6.12.31; 6.13 up to, but not including, 6.14.9; 6.155.4.294, 5.10.238, 5.15.185, 6.1.141, 6.6.93, 6.12.31
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: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and sch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may trigger an immediate dequeue and potential packet drop. In such cases, qdisc_tree_reduce_backlog() is called, but the HFSC qdisc's qlen and backlog have not yet been updated, leading to inconsistent queue accounting. This can leave an empty HFSC class in the active list, causing further consequences like use-after-free. This patch fixes the bug by moving the increment of sch->q.qlen and sch->qstats.backlog before the call to the child qdisc's peek() operation. This ensures that queue length and backlog are always accurate when packet drops or dequeues are triggered during the peek.

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

Recent Use After Free vulnerabilities

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