CVE-2025-37797

high

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

https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283

https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5

https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0

https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c

https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f

https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de

https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677

https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9

Details

Source: Mitre, NVD

Published: 2025-05-02

Updated: 2025-05-05

Risk Information

CVSS v2

Base Score: 4.6

Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:P/A:P

Severity: Medium

CVSS v3

Base Score: 7.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Severity: High

EPSS

EPSS: 0.00024