Description
In the Linux kernel, the following vulnerability has been resolved: net_sched: qfq: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of qfq, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. This patch checks whether the class was already added to the agg->active list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
Affected products
linux: linux kernel; debian: debian linux
References10
- git.kernel.org/stable/c/005a479540478a820c52de098e5e767e63e36f0a Patch
- git.kernel.org/stable/c/041f410aec2c1751ee22b8b73ba05d38c3a6a602 Patch
- git.kernel.org/stable/c/0aa23e0856b7cedb3c88d8e3d281c212c7e4fbeb Patch
- git.kernel.org/stable/c/0bf32d6fb1fcbf841bb9945570e0e2a70072c00f Patch
- git.kernel.org/stable/c/370218e8ce711684acc4cdd3cc3c6dd7956bc165 Patch
- git.kernel.org/stable/c/53bc0b55178bd59bdd4bcd16349505cabf54b1a2 Patch
- git.kernel.org/stable/c/a43783119e01849fbf2fe8855634e8989b240cb4 Patch
- git.kernel.org/stable/c/f139f37dcdf34b67f5bf92bc8e0f7f6b3ac63aa4 Patch
- lists.debian.org/debian-lts-announce/2025/08/msg00010.html Mailing List
- lists.debian.org/debian-lts-announce/2025/10/msg00007.html Mailing List
Metrics
- CVSS 3.1
-
7.8
HIGH
Score source: NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 0% percentile: 15 · as of 7 November 2026
- CWE
- CWE-415
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.