CVE-2026-64543: tipc: fix use-after-free of the discoverer in tipc_disc_rcv()
In the Linux kernel, the following vulnerability has been resolved:
tipc: fix use-after-free of the discoverer in tipcdiscrcv()
bearerdisable() frees b->disc with tipcdiscdelete()'s plain kfree(), but tipcdiscrcv() still dereferences b->disc in RX softirq under rcureadlock() (tipcudprecv -> tipcrcv -> tipcdiscrcv).
L2 bearers are safe thanks to the synchronizenet() in tipcdisablel2media(), but the UDP bearer defers that call to the cleanupbearer() workqueue, so the discoverer is freed with no grace period:
BUG: KASAN: slab-use-after-free in tipcdiscrcv (net/tipc/discover.c:149) Read of size 8 at addr ffff88802348b728 by task poctipc/184 <IRQ> tipcdiscrcv (net/tipc/discover.c:149) tipcrcv (net/tipc/node.c:2126) tipcudprecv (net/tipc/udpmedia.c:391) udprcv (net/ipv4/udp.c:2643) iplocaldeliverfinish (net/ipv4/ipinput.c:241) </IRQ> Freed by task 181: kfree (mm/slub.c:6565) bearerdisable (net/tipc/bearer.c:418) tipcnlbearerdisable (net/tipc/bearer.c:1001)
The bearer is freed with kfreercu(); free the discoverer the same way. Add an rcuhead to struct tipcdiscoverer and free it and its skb from an RCU callback.
Because the RCU callback (tipcdiscfreercu) lives in module text, a callrcu() that is still pending when the tipc module is unloaded would invoke a freed function. Add an rcubarrier() to tipcexit() after the bearer subsystem has been torn down, so all pending discoverer callbacks have run before the module text goes away.
Reachable from an unprivileged user namespace: the TIPCv2 genl family is netnsok and its bearer commands have no GENLADMINPERM. Needs CONFIGTIPC and CONFIGTIPCMEDIAUDP.
Affected Software
Remediation
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Event History
Frequently Asked Questions
What is the severity of CVE-2026-64543?
The severity of CVE-2026-64543 is rated at 57.
How do I fix CVE-2026-64543?
To fix CVE-2026-64543, update to the patched version of the Linux kernel that addresses the use-after-free vulnerability.
What is the nature of the vulnerability described in CVE-2026-64543?
CVE-2026-64543 is a use-after-free vulnerability in the Linux kernel related to the tipc_disc_rcv() function.
Which component of the Linux kernel is affected by CVE-2026-64543?
CVE-2026-64543 affects the TIPC (Transparent Inter-Process Communication) component of the Linux kernel.
Is CVE-2026-64543 exploitable remotely?
Yes, CVE-2026-64543 can potentially be exploited remotely due to the nature of the vulnerability in the networking code.