| Name | CVE-2025-37797 |
| 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. |
| Source | CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DLA-4178-1, DLA-4193-1 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| linux (PTS) | bullseye | 5.10.223-1 | vulnerable |
| bullseye (security) | 5.10.237-1 | fixed | |
| bookworm | 6.1.137-1 | fixed | |
| bookworm (security) | 6.1.140-1 | fixed | |
| trixie | 6.12.30-1 | fixed | |
| trixie (security) | 6.12.31-1 | fixed | |
| sid | 6.12.32-1 | fixed | |
| linux-6.1 (PTS) | bullseye (security) | 6.1.137-1~deb11u1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| linux | source | bullseye | 5.10.237-1 | DLA-4178-1 | ||
| linux | source | bookworm | 6.1.137-1 | |||
| linux | source | (unstable) | 6.12.27-1 | |||
| linux-6.1 | source | bullseye | 6.1.137-1~deb11u1 | DLA-4193-1 |
https://git.kernel.org/linus/3df275ef0a6ae181e8428a6589ef5d5231e58b5c (6.15-rc4)