CyberSecBulletin
CVE-2025-37890NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2025-37890 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 273bbcfa53541cde38b2003ad88a59b770306421, e0cf8ee23e1915431f262a7b2dee0c7a7d699af0, e3e949a39a91d1f829a4890e7dfe9417ac72e4d0 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 0.22% 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 273bbcfa53541cde38b2003ad88a59b770306421 or e0cf8ee23e1915431f262a7b2dee0c7a7d699af0 or e3e949a39a91d1f829a4890e7dfe9417ac72e4d0 or 8df7d37d626430035b413b97cee18396b3450bef, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.4.294 or 5.10.238 or 5.15.182 or 6.1.138, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, 273bbcfa53541cde38b2003ad88a59b770306421; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, e0cf8ee23e1915431f262a7b2dee0c7a7d699af0; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, e3e949a39a91d1f829a4890e7dfe9417ac72e4d0; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, 8df7d37d626430035b413b97cee18396b3450bef; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, 6082a87af4c52f58150d40dec1716011d871ac21; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, 2e7093c7a8aba5d4f8809f271488e5babe75e202; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, ac39fd4a757584d78ed062d4f6fd913f83bd98b5; 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea up to, but not including, 141d34391abbb315d68556b7c67ad97885407547; and 1 more ranges273bbcfa53541cde38b2003ad88a59b770306421, e0cf8ee23e1915431f262a7b2dee0c7a7d699af0, e3e949a39a91d1f829a4890e7dfe9417ac72e4d0, 8df7d37d626430035b413b97cee18396b3450bef, 6082a87af4c52f58150d40dec1716011d871ac21, 2e7093c7a8aba5d4f8809f271488e5babe75e202
LinuxLinux Kernel5.0.1 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, 5.15.182; 5.16 up to, but not including, 6.1.138; 6.2 up to, but not including, 6.6.90; 6.7 up to, but not including, 6.12.28; 6.13 up to, but not including, 6.14.6; 5.0; and 1 more ranges5.4.294, 5.10.238, 5.15.182, 6.1.138, 6.6.90, 6.12.28
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: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case). This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

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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