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Unrated severityNVD Advisory· Published May 2, 2025· Updated Nov 3, 2025

net_sched: hfsc: Fix a UAF vulnerability in class handling

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.

Affected products

345

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

8

News mentions

0

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