CVE-2026-68284
In the Linux kernel, the following vulnerability has been resolved:
bpf, sockmap: Fix cork use-after-free in tcp_bpf_sendmsg()
tcp_bpf_sendmsg() keeps msg_tx across sk_stream_wait_memory(), which
drops and reacquires the socket lock. Its error path tries to decide
whether msg_tx names the local temporary message by comparing it with
the current value of psock->cork.
This comparison is unsafe when two threads send on the same socket:
Thread A Thread B
msg_tx = psock->cork
sk_msg_alloc() fails
sk_stream_wait_memory()
releases the socket lock acquires the socket lock
completes the cork
psock->cork = NULL
frees the cork
reacquires the socket lock
msg_tx != psock->cork
sk_msg_free(msg_tx)
The stale cork is therefore mistaken for the local temporary message
and freed again. KASAN reported:
BUG: KASAN: slab-use-after-free in sk_msg_free+0x49/0x50
Read of size 4 at addr ffff88810c908800 by task poc/90
Call Trace:
sk_msg_free+0x49/0x50
tcp_bpf_sendmsg+0x14f5/0x1cc0
__sys_sendto+0x32c/0x3a0
__x64_sys_sendto+0xdb/0x1b0
Allocated by task 89:
__kasan_kmalloc+0x8f/0xa0
tcp_bpf_sendmsg+0x16b3/0x1cc0
Freed by task 91:
__kasan_slab_free+0x43/0x70
kfree+0x131/0x3c0
tcp_bpf_sendmsg+0xec3/0x1cc0
msg_tx can only name the stack-local tmp or the shared cork. Check for
tmp directly so a changed psock->cork cannot turn a shared message into
an apparent local one.
CSIRTS triage
- What
- Use-after-free vulnerability in TCP BPF sockmap cork handling during message sending.
- Who is affected
- Systems running affected Linux kernel versions with BPF sockmap enabled.
- Urgency
- High severity with potential for memory corruption; not currently exploited.
- Action
- Apply kernel patch or update to a fixed version once released.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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