CVE-2026-23270

NameCVE-2026-23270
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks As Paolo said earlier [1]: "Since the blamed commit below, classify can return TC_ACT_CONSUMED while the current skb being held by the defragmentation engine. As reported by GangMin Kim, if such packet is that may cause a UaF when the defrag engine later on tries to tuch again such packet." act_ct was never meant to be used in the egress path, however some users are attaching it to egress today [2]. Attempting to reach a middle ground, we noticed that, while most qdiscs are not handling TC_ACT_CONSUMED, clsact/ingress qdiscs are. With that in mind, we address the issue by only allowing act_ct to bind to clsact/ingress qdiscs and shared blocks. That way it's still possible to attach act_ct to egress (albeit only with clsact). [1] https://lore.kernel.org/netdev/674b8cbfc385c6f37fb29a1de08d8fe5c2b0fbee.1771321118.git.pabeni@redhat.com/ [2] https://lore.kernel.org/netdev/cc6bfb4a-4a2b-42d8-b9ce-7ef6644fb22b@ovn.org/
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDLA-4561-1, DSA-6238-1, DSA-6243-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
linux (PTS)bullseye5.10.223-1fixed
bullseye (security)5.10.251-5fixed
bookworm6.1.170-3fixed
bookworm (security)6.1.172-1fixed
trixie6.12.86-1fixed
trixie (security)6.12.88-1fixed
forky, sid7.0.7-1fixed
linux-6.1 (PTS)bullseye (security)6.1.172-1~deb11u1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
linuxsourcebullseye(not affected)
linuxsourcebookworm6.1.170-1DSA-6243-1
linuxsourcetrixie6.12.85-1DSA-6238-1
linuxsource(unstable)6.19.8-1
linux-6.1sourcebullseye6.1.170-1~deb11u1DLA-4561-1

Notes

[bullseye] - linux <not-affected> (Vulnerable code not present)
https://git.kernel.org/linus/11cb63b0d1a0685e0831ae3c77223e002ef18189 (7.0-rc3)

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