CVE-2026-64554

In the Linux kernel, the following vulnerability has been resolved:

netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment()

br_ip6_fragment() gets prevhdr, a pointer into the skb head, from

ip6_find_1stfragopt(), then calls skb_checksum_help(). For a cloned skb

skb_checksum_help() reallocates the head via pskb_expand_head(), leaving

prevhdr dangling. It is later dereferenced in ip6_frag_next(), causing a

use-after-free write.

Save prevhdr's offset before skb_checksum_help() and recompute it after,

like commit ef0efcd3bd3f ("ipv6: Fix dangling pointer when ipv6

fragment").

BUG: KASAN: slab-use-after-free in ip6_frag_next (net/ipv6/ip6_output.c:857)

Write of size 1 at addr ffff888013ff5016 by task exploit/141

Call Trace:

...

kasan_report (mm/kasan/report.c:595)

ip6_frag_next (net/ipv6/ip6_output.c:857)

br_ip6_fragment (net/ipv6/netfilter.c:212)

nf_ct_bridge_post (net/bridge/netfilter/nf_conntrack_bridge.c:407)

nf_hook_slow (net/netfilter/core.c:619)

br_forward_finish (net/bridge/br_forward.c:66)

__br_forward (net/bridge/br_forward.c:115)

maybe_deliver (net/bridge/br_forward.c:191)

br_flood (net/bridge/br_forward.c:245)

br_handle_frame_finish (net/bridge/br_input.c:229)

br_handle_frame (net/bridge/br_input.c:442)

...

packet_sendmsg (net/packet/af_packet.c:3114)

...

do_syscall_64 (arch/x86/entry/syscall_64.c:94)

entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

Kernel panic - not syncing: Fatal exception in interrupt