xfrm: use hlist_del_init_rcu for state_cache and state_cache_input

Summary

In the Linux kernel, the following vulnerability has been resolved: xfrm: use hlist_del_init_rcu for state_cache and state_cache_input Commit 14acf9652e56 ("xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete") converted bydst/bysrc/byseq/byspi from hlist_del_rcu() to hlist_del_init_rcu() so that a second __xfrm_state_delete() on the same object becomes a no-op rather than a write through LIST_POISON pprev. It missed state_cache and state_cache_input, which kept hlist_del_rcu(): • hlist_del_rcu() leaves pprev = LIST_POISON2 (non-NULL), so hlist_unhashed() returns false. • hlist_del_init_rcu() leaves pprev = NULL, so hlist_unhashed() returns true. A second __xfrm_state_delete() therefore enters __hlist_del() on the already-deleted state_cache/state_cache_input nodes and does WRITE_ONCE(*pprev, next) through LIST_POISON2 — a write use-after-free once the slab is reused. The corruption can in turn cause a subsequent hlist_for_each_entry_rcu traversal to follow a dangling next pointer, producing the read use-after-free reported in xfrm_input_state_lookup(). Switch state_cache and state_cache_input to hlist_del_init_rcu() to match the other four lists, closing the write use-after-free and, with it, the read use-after-free it spawns.

Timeline

1. Oct 6, 2026, 8:45 AM UTCCVE published
2. Oct 19, 2026, 9:16 AM UTCRecord last updated

Affected versions

• Linux Linux

  From aa48a18fdb0911572d133057cd579db704b87da4 · fixed in fb38fb7420d5f7192f9e2b6ac835ede149cd7ac5; From 0045e3d80613cc7174dc15f189ee6fc4e73b9365 · fixed in 4748c27e2e6a1969e02f1df46e62f79d2799b80b; From 0045e3d80613cc7174dc15f189ee6fc4e73b9365 · fixed in 9b74a47a4cbd0d29faff4f3b199212c73e6b6220; From 0045e3d80613cc7174dc15f189ee6fc4e73b9365 · fixed in 2afb8dc1f4390f164db8352f8e685e126e9db566; From 6.12.13 · fixed in 6.12.112

• Linux Linux

  6.13

• KernelLinux

  fixed in 6.12.112; From 6.13.0 · fixed in 6.18.54; fixed in 7.2.8

References 4