{"id":"DEBIAN-CVE-2026-64543","details":"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-\u003edisc with tipc_disc_delete()'s plain kfree(), but tipc_disc_rcv() still dereferences b-\u003edisc in RX softirq under rcu_read_lock() (tipc_udp_recv -\u003e tipc_rcv -\u003e 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  \u003cIRQ\u003e   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)  \u003c/IRQ\u003e  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.","modified":"2026-09-08T17:00:10.234295485Z","published":"2026-07-27T21:17:06.850Z","upstream":["CVE-2026-64543"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-64543"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.187-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.176-1","6.1.177-1","6.1.180-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not 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