GHSA-VFVW-GP7Q-PGRC
Vulnerability from github – Published: 2026-07-27 21:31 – Updated: 2026-08-19 18:32In 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 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) 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.
{
"affected": [],
"aliases": [
"CVE-2026-64543"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-27T21:17:06Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix use-after-free of the discoverer in tipc_disc_rcv()\n\nbearer_disable() frees b-\u003edisc with tipc_disc_delete()\u0027s plain kfree(),\nbut tipc_disc_rcv() still dereferences b-\u003edisc in RX softirq under\nrcu_read_lock() (tipc_udp_recv -\u003e tipc_rcv -\u003e tipc_disc_rcv).\n\nL2 bearers are safe thanks to the synchronize_net() in\ntipc_disable_l2_media(), but the UDP bearer defers that call to the\ncleanup_bearer() workqueue, so the discoverer is freed with no grace\nperiod:\n\n BUG: KASAN: slab-use-after-free in tipc_disc_rcv (net/tipc/discover.c:149)\n Read of size 8 at addr ffff88802348b728 by task poc_tipc/184\n \u003cIRQ\u003e\n tipc_disc_rcv (net/tipc/discover.c:149)\n tipc_rcv (net/tipc/node.c:2126)\n tipc_udp_recv (net/tipc/udp_media.c:391)\n udp_rcv (net/ipv4/udp.c:2643)\n ip_local_deliver_finish (net/ipv4/ip_input.c:241)\n \u003c/IRQ\u003e\n Freed by task 181:\n kfree (mm/slub.c:6565)\n bearer_disable (net/tipc/bearer.c:418)\n tipc_nl_bearer_disable (net/tipc/bearer.c:1001)\n\nThe bearer is freed with kfree_rcu(); free the discoverer the same way.\nAdd an rcu_head to struct tipc_discoverer and free it and its skb from an\nRCU callback.\n\nBecause the RCU callback (tipc_disc_free_rcu) lives in module text, a\ncall_rcu() that is still pending when the tipc module is unloaded would\ninvoke a freed function. Add an rcu_barrier() to tipc_exit() after the\nbearer subsystem has been torn down, so all pending discoverer callbacks\nhave run before the module text goes away.\n\nReachable from an unprivileged user namespace: the TIPCv2 genl family is\nnetnsok and its bearer commands have no GENL_ADMIN_PERM. Needs CONFIG_TIPC\nand CONFIG_TIPC_MEDIA_UDP.",
"id": "GHSA-vfvw-gp7q-pgrc",
"modified": "2026-08-19T18:32:02Z",
"published": "2026-07-27T21:31:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64543"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1579342d71133da7f00daa02c75cebec7372097b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/380413cdfd29fb9fa486c82889132b680c4983c5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4da2ac7749411971e1b222b992da5a172ce45f98"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5e215bf1c47fdddf8203a0fe80a0ed594065f101"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a0c5fdeb5fa257f8c6d469af266bc087cb5de6a2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b65289e1c3f352a9f92c6e19713ddd647e033253"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ec7d54d8cc1723921d671e3272b427c96366506f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f05b3f4c78370469286879c765f5a1dd39dbcd32"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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