CVE-2025-37797: Linux kernel · Use After Free
Source GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 4 Nov 2026, 17:16 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 2 May 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 4 Nov 2026.
Description
In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class handling This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class handling. The issue occurs due to a time-of-check/time-of-use condition in hfsc_change_class() when working with certain child qdiscs like netem or codel. The vulnerability works as follows: 1. hfsc_change_class() checks if a class has packets (q.qlen != 0) 2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g., codel, netem) might drop packets and empty the queue 3. The code continues assuming the queue is still non-empty, adding the class to vttree 4. This breaks HFSC scheduler assumptions that only non-empty classes are in vttree 5. Later, when the class is destroyed, this can lead to a Use-After-Free The fix adds a second queue length check after qdisc_peek_len() to verify the queue wasn't emptied.
References
- nvd.nist.gov/vuln/detail/CVE-2025-37797 (opens in a new tab)
- git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9 (opens in a new tab)
- git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677 (opens in a new tab)
- git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de (opens in a new tab)
- git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f (opens in a new tab)
- git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c (opens in a new tab)
- git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0 (opens in a new tab)
- git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5 (opens in a new tab)
- git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/05/msg00030.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/05/msg00045.html (opens in a new tab)