CVE-2025-37798: Linux kernel · codel: remove sch->q.qlen check before qdisc_tree_reduce_backlog()
Source GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 4 Nov 2026, 18:35 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.
What to do
AI-suggested
A fix has been implemented in the Linux kernel by removing the unsafe sch->q.qlen check after making qlen_notify() callbacks idempotent. Users should update their Linux kernel to the fixed version once it is available.
Description
CVE-2025-37798 is a high-severity vulnerability in the Linux kernel related to the CoDel (Controlled Delay) queuing discipline. The issue involved an unsafe check of the queue length (sch->q.qlen) before calling qdisc_tree_reduce_backlog(). This check was removed after making all qlen_notify() callbacks idempotent, which resolved the vulnerability.
References
- nvd.nist.gov/vuln/detail/CVE-2025-37798 (opens in a new tab)
- git.kernel.org/stable/c/2f9761a94bae33d26e6a81b31b36e7d776d93dc1 (opens in a new tab)
- git.kernel.org/stable/c/342debc12183b51773b3345ba267e9263bdfaaef (opens in a new tab)
- git.kernel.org/stable/c/4d55144b12e742404bb3f8fee6038bafbf45619d (opens in a new tab)
- git.kernel.org/stable/c/7a742a9506849d1c1aa71e36c89855ceddc7d58e (opens in a new tab)
- git.kernel.org/stable/c/829c49b6b2ff45b043739168fd1245e4e1a91a30 (opens in a new tab)
- git.kernel.org/stable/c/a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31 (opens in a new tab)
- git.kernel.org/stable/c/cc71a757da78dd4aa1b4a9b19cb011833730ccf2 (opens in a new tab)
- git.kernel.org/stable/c/e73c838c80dccb9e4f19becc11d9f3cb4a27d483 (opens in a new tab)
- git.kernel.org/stable/c/eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/05/msg00045.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00007.html (opens in a new tab)