Linux kernel netfilter ctnetlink out-of-bounds read on new expectations
CVE-2026-43025 is a Linux kernel vulnerability in the netfilter ctnetlink expectation-handling path. The issue occurs when userspace creates a new expectation and supplies an explicit helper that differs from the helper associated with the existing master conntrack entry. During validation of CTA_EXPECT_CLASS, this mismatch can lead to a slab out-of-bounds read in nf_ct_expect_related_report(), as shown by the reported KASAN trace through ctnetlink_create_expect() and ctnetlink_new_expect(). The result is that the kernel may read memory beyond the expectation object boundary. The fix changes ctnetlink to ignore an explicit helper provided by userspace for new expectations and instead use the existing master conntrack helper. CTA_EXPECT_HELP_NAME remains available for exposing helper names to userspace via netlink dump.
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