CVE-2026-23270

net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks

State: Published
Severity: 7.8 High
Published: Mar 18, 2026
Updated: Oct 19, 2026
Reserved: Jan 13, 2026

Description

In 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/

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

CWE-416 Use After Free

Affected Products

Product	Versions
LinuxLinux	172ba7d46c202e679f3ccb10264c67416aaeb1c4 to before bc4e5bb529823a09f02dbe96169de679a9db26e0Affected 0b5b831122fc3789fff75be433ba3e4dd7b779d4 to before fb3c380a54e33d1fd272cc342faa906d787d7ef1Affected 73f7da5fd124f2cda9161e2e46114915e6e82e97 to before 5a110ddcc99bda77a28598b3555fe009eaab3828Affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 524ce8b4ea8f64900b6c52b6a28df74f6bc0801eAffected 3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 380ad8b7c65ea7aa10ef2258297079ed5ac1f5b6Affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 9deda0fcda5c1f388c5e279541850b71a2ccfcf4Affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 11cb63b0d1a0685e0831ae3c77223e002ef18189Affected f5346df0591d10bc948761ca854b1fae6d2ef441Affected 5.15.148 to before 5.15.203Affected 6.1.75 to before 6.1.167Affected 6.6.14 to before 6.6.130Affected 6.7.2 to before 6.8Affected
LinuxLinux	6.8Affected before 6.8Not affected 5.15.203 through 5.15.Not affected 6.1.167 through 6.1.Not affected 6.6.130 through 6.6.Not affected 6.12.77 through 6.12.Not affected 6.18.18 through 6.18.Not affected 6.19.8 through 6.19.Not affected 7.0 and laterNot affected

Product

Versions

LinuxLinux

172ba7d46c202e679f3ccb10264c67416aaeb1c4 to before bc4e5bb529823a09f02dbe96169de679a9db26e0Affected
0b5b831122fc3789fff75be433ba3e4dd7b779d4 to before fb3c380a54e33d1fd272cc342faa906d787d7ef1Affected
73f7da5fd124f2cda9161e2e46114915e6e82e97 to before 5a110ddcc99bda77a28598b3555fe009eaab3828Affected
3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 524ce8b4ea8f64900b6c52b6a28df74f6bc0801eAffected
3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 380ad8b7c65ea7aa10ef2258297079ed5ac1f5b6Affected
3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 9deda0fcda5c1f388c5e279541850b71a2ccfcf4Affected
3f14b377d01d8357eba032b4cabc8c1149b458b6 to before 11cb63b0d1a0685e0831ae3c77223e002ef18189Affected
f5346df0591d10bc948761ca854b1fae6d2ef441Affected
5.15.148 to before 5.15.203Affected
6.1.75 to before 6.1.167Affected
6.6.14 to before 6.6.130Affected
6.7.2 to before 6.8Affected

LinuxLinux

6.8Affected
before 6.8Not affected
5.15.203 through 5.15.*Not affected
6.1.167 through 6.1.*Not affected
6.6.130 through 6.6.*Not affected
6.12.77 through 6.12.*Not affected
6.18.18 through 6.18.*Not affected
6.19.8 through 6.19.*Not affected
7.0 and laterNot affected

References

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