CVE-2025-21703
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.29%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.29% probability · 21th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-416
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- 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
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.