Use After Free Affecting kernel-rt-core package, versions *


Severity

Recommended
medium

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.06% (20th percentile)

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  • Snyk IDSNYK-RHEL9-KERNELRTCORE-10025706
  • published5 May 2025
  • disclosed2 May 2025

Introduced: 2 May 2025

CVE-2025-37797  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:9 kernel-rt-core.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-core package and not the kernel-rt-core package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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 Base Scores

version 3.1