CVE-2025-21703
HIGH severity · CVSS 7.8 · Use-after-free
7.8CVSS HIGH
Summary
In the Linux kernel, the following vulnerability has been resolved: netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() qdisc_tree_reduce_backlog() notifies parent qdisc only if child qdisc becomes empty, therefore we need to reduce the backlog of the child qdisc before calling it. Otherwise it would miss the opportunity to call cops->qlen_notify(), in the case of DRR, it resulted in UAF since DRR uses ->qlen_notify() to maintain its active list.
Impact & exploitability
Attack vectorLocal
Attack complexityLow
Privileges requiredLow
User interactionNone
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
Exploit probability (EPSS)0%
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected products we track (1)
Recommendation
Apply the vendor fix promptly. Open any affected product above for its exact safe version.
Official patch: https://git.kernel.org/stable/c/1f8e3f4a4b8b90ad274dfbc66fc7d55cb582f4d5 ↗
Additional information
- NVD record
- https://git.kernel.org/stable/c/1f8e3f4a4b8b90ad274dfbc66fc7d55cb582f4d5Patch
- https://git.kernel.org/stable/c/6312555249082d6d8cc5321ff725df05482d8b83Patch
- https://git.kernel.org/stable/c/638ba5089324796c2ee49af10427459c2de35f71Patch
- https://git.kernel.org/stable/c/7b79ca9a1de6a428d486ff52fb3d602321c08f55Patch
- https://git.kernel.org/stable/c/7f31d74fcc556a9166b1bb20515542de7bb939d1Patch
- https://git.kernel.org/stable/c/839ecc583fa00fab785fde1c85a326743657fd32Patch
- https://git.kernel.org/stable/c/98a2c685293aae122f688cde11d9334dddc5d207Patch
- https://git.kernel.org/stable/c/e395fec75ac2dbffc99b4bce57b7f1f3c5449f2cPatch