CVE-2025-37797

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.

• linux linux kernel (>= 4.14.1 < 5.4.293) • linux linux kernel (>= 5.5 < 5.10.237) • linux linux kernel (>= 5.11 < 5.15.181) • linux linux kernel (>= 5.16 < 6.1.136) • linux linux kernel (>= 6.2 < 6.6.89) • linux linux kernel (>= 6.7 < 6.12.26) • linux linux kernel (>= 6.13 < 6.14.5) • linux linux kernel 4.14 • linux linux kernel 6.15 • debian debian linux 11.0