CVE-2026-64541: net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket
In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix UAF in smccdcrxhandler() by pinning the socket
smccdcrxhandler() looks up the connection by token under the link group's connslock, drops the lock, and then dereferences conn and the smcsock derived from it, ending in sockhold(&smc->sk) inside smccdcmsgrecv(). No reference is held across the lock release.
The only reference pinning the socket while the connection is discoverable in the link group is taken in smclgrregisterconn() (sockhold) and dropped in smclgrunregisterconn() (sockput), both under connslock. Once the handler drops connslock, a concurrent close() -> smcrelease() -> smcconnfree() -> smclgrunregisterconn() can drop that reference and free the smcsock, so the handler's later sockhold() runs on freed memory:
WARNING: lib/refcount.c:25 at refcountwarnsaturate Workqueue: rxewq dowork refcountwarnsaturate (lib/refcount.c:25) smccdcmsgrecv (net/smc/smccdc.c:430) smccdcrxhandler (net/smc/smccdc.c:502) smcwrrxtaskletfn (net/smc/smcwr.c:445) taskletactioncommon (kernel/softirq.c:938) handlesoftirqs (kernel/softirq.c:622) Kernel panic - not syncing: paniconwarn set
Only SMC-R is affected. The SMC-D receive tasklet is stopped by taskletkill(&conn->rxtsklet) in smcconnfree() before the connection is unregistered, so it cannot run concurrently with the free.
Take the socket reference while still holding connslock, so the registration reference can no longer be the last one, and drop it once the handler is done.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Event History
Frequently Asked Questions
What is the severity of CVE-2026-64541?
The severity of CVE-2026-64541 is critical with a CVSS score of 9.8.
How do I fix CVE-2026-64541?
To fix CVE-2026-64541, ensure that your Linux kernel is updated to the latest version that includes the patch for this vulnerability.
What does CVE-2026-64541 affect?
CVE-2026-64541 affects the Linux kernel, specifically the socket management code in the net/smc module.
What is the risk associated with CVE-2026-64541?
CVE-2026-64541 has a risk rating of 86, indicating a critical threat level due to potential unauthorized access.
Is CVE-2026-64541 exploitable remotely?
Yes, CVE-2026-64541 is remotely exploitable, as indicated by its vector score that includes network access.