{
  "containers": {
    "cna": {
      "affected": [
        {
          "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",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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, \u0026ub-\u003ercast.list, list) {\n\t\tdst_cache_destroy(\u0026rcast-\u003edst_cache);\n\t\tlist_del_rcu(\u0026rcast-\u003elist);\n\t\tkfree_rcu(rcast, rcu);\n\t}\n...\n\tdst_cache_destroy(\u0026ub-\u003ercast.dst_cache);\n\tudp_tunnel_sock_release(ub-\u003esk);\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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is in cleanup_bearer() during UDP bearer teardown, reached only via TIPC genetlink bearer disable (TIPC_NL_BEARER_DISABLE) or network-namespace exit; remote UDP/TIPC peers cannot initiate teardown, so exploitation requires local netlink/netns access even though concurrent xmit/recv may involve network I/O.\nAC:L - An attacker with namespace CAP_NET_ADMIN can script both teardown and concurrent traffic (enable/disable bearer or destroy netns while sending/receiving TIPC UDP on port 6118), controlling both sides of the RCU race; dst_cache_destroy()\u0027s free_percpu() widens the window and syzbot triggered it reliably.\nPR:L - Bearer disable/enable and netns teardown require CAP_NET_ADMIN; TIPC genetlink ops use GENL_UNS_ADMIN_PERM and tipc_genl_family.netnsok=true, so unprivileged users obtain effective net-admin capability via user/network namespaces (unshare -Urn).\nUI:N - Exploitation needs no victim interaction beyond the attacker\u0027s own namespace/netlink operations and packet generation; no mount, file open, or other user-directed action is required.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security domain; impacts are kernel crash or local privilege escalation, not VM escape or cross-security-authority boundary crossing.\nC:H - Premature dst_cache_destroy() frees per-CPU cache memory while concurrent tipc_udp_xmit() may call dst_cache_get() on the freed object, and the post-synchronize_net() recv path dereferences freed udp_bearer, enabling kernel memory disclosure.\nI:H - UAF on dst_cache structures and udp_bearer allows heap shaping and control of freed-object contents, providing primitives for arbitrary kernel writes and potential control-flow hijacking/local privilege escalation.\nA:H - Concurrent use-after-free reliably causes kernel oops/panic (per commit: UAF on per-CPU cache pointer crashes) and can be triggered repeatedly during scripted bearer teardown loops."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:43:44.084Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72404",
    "datePublished": "2026-08-15T05:56:28.124Z",
    "dateReserved": "2026-08-09T03:40:39.925Z",
    "dateUpdated": "2026-08-17T05:43:44.084Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}