CVE-2025-37797net_sched: hfsc: Fix a UAF vulnerability in class handling
- 7.8HighCVSS base score
- 0.22%Exploitation in 30 daysEPSS · top 87% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By Linux
- 16 days later
· 16 days later
Published
- 15 months later
· 15 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Modified | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.22% · top 87% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < 28b09a067831f7317c3841812276022d6c940677
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < 39b9095dd3b55d9b2743df038c32138efa34a9de
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < fcc8ede663569c704fb00a702973bd6c00373283
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < 20d584a33e480ae80d105f43e0e7b56784da41b9
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < 3aa852e3605000d5c47035c3fc3a986d14ccfa9f
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < 86cd4641c713455a4f1c8e54c370c598c2b1cee0
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < bb583c88d23b72d8d16453d24856c99bd93dadf5
- affected 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 – < 3df275ef0a6ae181e8428a6589ef5d5231e58b5c
- affected 4.14
- unaffected < 4.14
- unaffected 5.4.293 – ≤ 5.4.*
- unaffected 5.10.237 – ≤ 5.10.*
- unaffected 5.15.181 – ≤ 5.15.*
- unaffected 6.1.136 – ≤ 6.1.*
- unaffected 6.6.89 – ≤ 6.6.*
- unaffected 6.12.26 – ≤ 6.12.*
- unaffected 6.14.5 – ≤ 6.14.*
- unaffected 6.15 – ≤ *
References
References10
- https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677 (opens in a new tab)
- https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de (opens in a new tab)
- https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283 (opens in a new tab)
- https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9 (opens in a new tab)
- https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f (opens in a new tab)
- https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0 (opens in a new tab)
- https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5 (opens in a new tab)
- https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-13245 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2025-37797)Record last updated .