CVE-2026-64543
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
A use-after-free vulnerability was found in the Linux kernel's TIPC subsystem in the tipc_disc_rcv() function. The bearer_disable() function frees the discoverer structure (b->disc) with kfree(), but tipc_disc_rcv() still dereferences it in RX softirq context, leading to a use-after-free. The issue affects the UDP bearer, which lacks a proper grace period before deallocation.
Risk Assessment
An unprivileged user namespace attacker can trigger a kernel panic or potentially escalate privileges by exploiting the use-after-free in the TIPC stack. The vulnerability requires CONFIG_TIPC and CONFIG_TIPC_MEDIA_UDP to be enabled.
Recommendation
Apply the Linux kernel patch that changes the tipc_discoverer deallocation to use kfree_rcu() and adds an rcu_barrier() in tipc_exit(). Update to a kernel version containing this fix as soon as possible.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: tipc: fix use-after-free of the discoverer in tipc_disc_rcv() bearer_disable() frees b->disc with tipc_disc_delete()'s plain kfree(), but tipc_disc_rcv() still dereferences b->disc in RX softirq under rcu_read_lock() (tipc_udp_recv -> tipc_rcv -> tipc_disc_rcv). L2 bearers are safe thanks to the synchronize_net() in tipc_disable_l2_media(), but the UDP bearer defers that call to the cleanup_bearer() workqueue, so the discoverer is freed with no grace period: BUG: KASAN: slab-use-after-free in tipc_disc_rcv (net/tipc/discover.c:149) Read of size 8 at addr ffff88802348b728 by task poc_tipc/184 <IRQ> tipc_disc_rcv (net/tipc/discover.c:149) tipc_rcv (net/tipc/node.c:2126) tipc_udp_recv (net/tipc/udp_media.c:391) udp_rcv (net/ipv4/udp.c:2643) ip_local_deliver_finish (net/ipv4/ip_input.c:241) </IRQ> Freed by task 181: kfree (mm/slub.c:6565) bearer_disable (net/tipc/bearer.c:418) tipc_nl_bearer_disable (net/tipc/bearer.c:1001) The bearer is freed with kfree_rcu(); free the discoverer the same way. Add an rcu_head to struct tipc_discoverer and free it and its skb from an RCU callback. Because the RCU callback (tipc_disc_free_rcu) lives in module text, a call_rcu() that is still pending when the tipc module is unloaded would invoke a freed function. Add an rcu_barrier() to tipc_exit() 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 GENL_ADMIN_PERM. Needs CONFIG_TIPC and CONFIG_TIPC_MEDIA_UDP.

