CVE-2026-72404 - Vulnerability Details

Vendors	Products
Linux Subscribe	Linux Kernel Subscribe

Link	Providers
https://git.kernel.org/stable/c/1c8393eefa3cadf4ca0b61119ad1321aa32d3c8c
https://git.kernel.org/stable/c/7116764ca53ff529335d7ab7c364a69f094b23a5

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: tipc: fix UAF in cleanup_bearer() due to premature dst_cache_destroy() TIPC UDP media bearer teardown calls dst_cache_destroy() on its replicast caches before calling synchronize_net() to wait for concurrent RCU readers (transmitters) to finish: static void cleanup_bearer(struct work_struct *work) { ... list_for_each_entry_safe(rcast, tmp, &ub->rcast.list, list) { dst_cache_destroy(&rcast->dst_cache); list_del_rcu(&rcast->list); kfree_rcu(rcast, rcu); } ... dst_cache_destroy(&ub->rcast.dst_cache); udp_tunnel_sock_release(ub->sk); synchronize_net(); ... } This is highly buggy because dst_cache_destroy() immediately frees the per-CPU cache memory (free_percpu()) and releases the cached dst entries without any synchronization. If a concurrent transmitter (e.g., tipc_udp_xmit()) is running on another CPU under RCU protection, it can call dst_cache_get() concurrently, leading to: 1. Use-After-Free on the per-CPU cache pointer itself (crash). 2. "rcuref - imbalanced put()" warning if it attempts to release a dst that was concurrently released by dst_cache_destroy(). Furthermore, calling kfree(ub) immediately after synchronize_net() without closing the socket first (or waiting after closing it) leaves a window where a concurrent receiver (tipc_udp_recv()) could start after synchronize_net(), access ub, and suffer a UAF when kfree(ub) runs. To fix this, we must defer dst_cache_destroy() and kfree(ub) until after we have ensured that no more readers can see the bearer/socket and all existing readers have finished: 1. Defer rcast entry destruction (both dst_cache_destroy() and kfree()) to an RCU callback using call_rcu_hurry(). Using call_rcu_hurry() ensures the dst entries are released quickly. 2. Release the bearer socket using udp_tunnel_sock_release() (stops new receive readers). 3. Call synchronize_net() to wait for all outstanding RCU readers (both transmit and receive) to finish. 4. Now that it is safe, call dst_cache_destroy() on the main bearer cache, and free ub. Note: 3) and 4) can be changed later in net-next to also use call_rcu_hurry() and get rid of the synchronize_net() latency.
Title		tipc: fix UAF in cleanup_bearer() due to premature dst_cache_destroy()
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/1c8393eefa3cadf4ca0b61119ad1321aa32d3c8c https://git.kernel.org/stable/c/7116764ca53ff529335d7ab7c364a69f094b23a5

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-72404", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.925Z", "datePublished": "2026-08-15T05:56:28.124Z", "dateUpdated": "2026-08-15T05:56:28.124Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-15T05:56:28.124Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix UAF in cleanup_bearer() due to premature dst_cache_destroy()\n\nTIPC UDP media bearer teardown calls dst_cache_destroy() on its\nreplicast caches before calling synchronize_net() to wait for\nconcurrent RCU readers (transmitters) to finish:\n\nstatic void cleanup_bearer(struct work_struct *work)\n{\n...\n\tlist_for_each_entry_safe(rcast, tmp, &ub->rcast.list, list) {\n\t\tdst_cache_destroy(&rcast->dst_cache);\n\t\tlist_del_rcu(&rcast->list);\n\t\tkfree_rcu(rcast, rcu);\n\t}\n...\n\tdst_cache_destroy(&ub->rcast.dst_cache);\n\tudp_tunnel_sock_release(ub->sk);\n\tsynchronize_net();\n...\n}\n\nThis is highly buggy because dst_cache_destroy() immediately frees the\nper-CPU cache memory (free_percpu()) and releases the cached dst\nentries without any synchronization.\n\nIf a concurrent transmitter (e.g., tipc_udp_xmit()) is running on another\nCPU under RCU protection, it can call dst_cache_get() concurrently,\nleading to:\n1. Use-After-Free on the per-CPU cache pointer itself (crash).\n2. \"rcuref - imbalanced put()\" warning if it attempts to release a\n dst that was concurrently released by dst_cache_destroy().\n\nFurthermore, calling kfree(ub) immediately after synchronize_net() without\nclosing the socket first (or waiting after closing it) leaves a window\nwhere a concurrent receiver (tipc_udp_recv()) could start after\nsynchronize_net(), access ub, and suffer a UAF when kfree(ub) runs.\n\nTo fix this, we must defer dst_cache_destroy() and kfree(ub) until after\nwe have ensured that no more readers can see the bearer/socket and all\nexisting readers have finished:\n\n1. Defer rcast entry destruction (both dst_cache_destroy() and kfree())\n to an RCU callback using call_rcu_hurry().\n Using call_rcu_hurry() ensures the dst entries are released quickly.\n\n2. Release the bearer socket using udp_tunnel_sock_release() (stops\n new receive readers).\n\n3. Call synchronize_net() to wait for all outstanding RCU readers\n (both transmit and receive) to finish.\n\n4. Now that it is safe, call dst_cache_destroy() on the main bearer\n cache, and free ub.\n\nNote: 3) and 4) can be changed later in net-next to also use\ncall_rcu_hurry() and get rid of the synchronize_net() latency."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/tipc/udp_media.c"], "versions": [{"version": "e9c1a793210f29f32ee4cf048e04d7d9bb3221cc", "lessThan": "1c8393eefa3cadf4ca0b61119ad1321aa32d3c8c", "status": "affected", "versionType": "git"}, {"version": "e9c1a793210f29f32ee4cf048e04d7d9bb3221cc", "lessThan": "7116764ca53ff529335d7ab7c364a69f094b23a5", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/tipc/udp_media.c"], "versions": [{"version": "5.3", "status": "affected"}, {"version": "0", "lessThan": "5.3", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2-rc1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "7.1.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "7.2-rc1"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/1c8393eefa3cadf4ca0b61119ad1321aa32d3c8c"}, {"url": "https://git.kernel.org/stable/c/7116764ca53ff529335d7ab7c364a69f094b23a5"}], "title": "tipc: fix UAF in cleanup_bearer() due to premature dst_cache_destroy()", "x_generator": {"engine": "bippy-1.2.0"}}}}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/tipc/udp_media.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "1c8393eefa3cadf4ca0b61119ad1321aa32d3c8c", "status": "affected", "version": "e9c1a793210f29f32ee4cf048e04d7d9bb3221cc", "versionType": "git"}, {"lessThan": "7116764ca53ff529335d7ab7c364a69f094b23a5", "status": "affected", "version": "e9c1a793210f29f32ee4cf048e04d7d9bb3221cc", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["net/tipc/udp_media.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.3"}, {"lessThan": "5.3", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "7.1.*", "status": "unaffected", "version": "7.1.5", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.2-rc1", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix UAF in cleanup_bearer() due to premature dst_cache_destroy()\n\nTIPC UDP media bearer teardown calls dst_cache_destroy() on its\nreplicast caches before calling synchronize_net() to wait for\nconcurrent RCU readers (transmitters) to finish:\n\nstatic void cleanup_bearer(struct work_struct *work)\n{\n...\n\tlist_for_each_entry_safe(rcast, tmp, &ub->rcast.list, list) {\n\t\tdst_cache_destroy(&rcast->dst_cache);\n\t\tlist_del_rcu(&rcast->list);\n\t\tkfree_rcu(rcast, rcu);\n\t}\n...\n\tdst_cache_destroy(&ub->rcast.dst_cache);\n\tudp_tunnel_sock_release(ub->sk);\n\tsynchronize_net();\n...\n}\n\nThis is highly buggy because dst_cache_destroy() immediately frees the\nper-CPU cache memory (free_percpu()) and releases the cached dst\nentries without any synchronization.\n\nIf a concurrent transmitter (e.g., tipc_udp_xmit()) is running on another\nCPU under RCU protection, it can call dst_cache_get() concurrently,\nleading to:\n1. Use-After-Free on the per-CPU cache pointer itself (crash).\n2. \"rcuref - imbalanced put()\" warning if it attempts to release a\n dst that was concurrently released by dst_cache_destroy().\n\nFurthermore, calling kfree(ub) immediately after synchronize_net() without\nclosing the socket first (or waiting after closing it) leaves a window\nwhere a concurrent receiver (tipc_udp_recv()) could start after\nsynchronize_net(), access ub, and suffer a UAF when kfree(ub) runs.\n\nTo fix this, we must defer dst_cache_destroy() and kfree(ub) until after\nwe have ensured that no more readers can see the bearer/socket and all\nexisting readers have finished:\n\n1. Defer rcast entry destruction (both dst_cache_destroy() and kfree())\n to an RCU callback using call_rcu_hurry().\n Using call_rcu_hurry() ensures the dst entries are released quickly.\n\n2. Release the bearer socket using udp_tunnel_sock_release() (stops\n new receive readers).\n\n3. Call synchronize_net() to wait for all outstanding RCU readers\n (both transmit and receive) to finish.\n\n4. Now that it is safe, call dst_cache_destroy() on the main bearer\n cache, and free ub.\n\nNote: 3) and 4) can be changed later in net-next to also use\ncall_rcu_hurry() and get rid of the synchronize_net() latency."}], "id": "CVE-2026-72404", "lastModified": "2026-08-15T06:22:13.970", "metrics": {}, "published": "2026-08-15T06:22:13.970", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/1c8393eefa3cadf4ca0b61119ad1321aa32d3c8c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7116764ca53ff529335d7ab7c364a69f094b23a5"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

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