net/sched: act_ct: fix helper UAF due to extensions realloc

Summary

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: fix helper UAF due to extensions realloc While calling the helpers, a raw pointer to the extensions area is wired into expectations list: -> nf_ct_helper() -> helper->help() -> nf_ct_expect_related_report() -> nf_ct_expect_insert() -> hlist_add_head_rcu(&exp->lnode, &master_help->expectations) In case the connection is not confirmed yet, more extensions can be added afterwards with *_ext_add() calls reallocating the extension space and leaving the now invalid pointer in the expectations list that is later accessed while removing the expectation. Make sure that helpers are called at the end after all the other extensions are already added. Note that the helper rejection now leaves the mark and labels set, but that's not different from how the NAT was handled before or how the mark and the labels were handled on confirmation failure. And there are no atomicity guarantees provided by the API anyway.

Timeline

1. Oct 18, 2026, 3:14 PM UTCCVE published
2. Oct 24, 2026, 2:08 PM UTCRecord last updated

Affected versions

• Linux Linux

  From a21b06e7319129994f339ed47f512bbe57b77f5b · fixed in 31f5fe29a572037ee19c233dfe506849940c484b; From a21b06e7319129994f339ed47f512bbe57b77f5b · fixed in 1679bbf5fbeac52a310b1a58b2b301bbf388bdbf; From a21b06e7319129994f339ed47f512bbe57b77f5b · fixed in 812c16a255e7773a544e88b39ae6daed25544d30; From a21b06e7319129994f339ed47f512bbe57b77f5b · fixed in 8988f4d11f3fba0ab38122178836c683ad516a05; From a21b06e7319129994f339ed47f512bbe57b77f5b · fixed in dad19b59da050cb60d3f7023dac2a042a84bf0bd

• Linux Linux

  6.2

• KernelLinux

  From 6.2.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.55; From 6.19.0 · fixed in 7.2.9

References 5