CVE-2025-37797

Advisory lineage Upstream: 0 Downstream: 134
Analyzed
Published: 02 May 2025, 14:16
Last modified:11 May 2026, 21:15

Vulnerability Summary

Overall Risk (default)
medium
31/100
CVSS Score
7.8 HIGH
v3.1 (nvd)
EPSS Score
0.08% LOW
0% probability +0.05%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

02 May 2025, 14:16
Published
Vulnerability first disclosed
11 May 2026, 21:15
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•HIGH•Score: 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.08%• Percentile: 24%

Techniques & Countermeasures

  • CWE-416•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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Affected Systems

  • debian•debian_linux

    11.0

  • linux•linux

    ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < 28b09a067831f7317c3841812276022d6c940677 | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < 39b9095dd3b55d9b2743df038c32138efa34a9de | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < fcc8ede663569c704fb00a702973bd6c00373283 | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < 20d584a33e480ae80d105f43e0e7b56784da41b9 | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < 3aa852e3605000d5c47035c3fc3a986d14ccfa9f | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < 86cd4641c713455a4f1c8e54c370c598c2b1cee0 | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < bb583c88d23b72d8d16453d24856c99bd93dadf5 | ≥ 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14, < 3df275ef0a6ae181e8428a6589ef5d5231e58b5c | 4.14

  • linux•linux_kernel

    ≥ 4.14.1, < 5.4.293 | ≥ 5.5, < 5.10.237 | ≥ 5.11, < 5.15.181 | ≥ 5.16, < 6.1.136 | ≥ 6.2, < 6.6.89 | ≥ 6.7, < 6.12.26 | ≥ 6.13, < 6.14.5 | 4.14 | 4.14:rc2 | 4.14:rc3 | 4.14:rc4 | 4.14:rc5 | 4.14:rc6 | 4.14:rc7 | 4.14:rc8 | 6.15:rc1 | 6.15:rc2 | 6.15:rc3

References (10)