{"id":"CVE-2026-74543","title":"net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()\n\nsyzbot reported a memory leak [1] in the UDP tunnel NIC offload code.\n\nWhen device registration fails (…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < 52c753b46265243406690d980faa9514d3f53827","Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < b712da45bd9b9835d132e9fbc0c3e43c164cb1fd","Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < f82a2ded3d7a9098267c84f14eafdb98c4550ac5","Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < b322532a4b774db1b480a2de84125910a70739a5","Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < 080695e6f005e2396f1207fd69d24c442cb230c6","Linux 5.9"],"published":"2026-08-15","updated":"2026-10-21","sourceUpdated":"2026-10-21T12:45:53.873Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74543","references":[{"url":"https://git.kernel.org/stable/c/52c753b46265243406690d980faa9514d3f53827"},{"url":"https://git.kernel.org/stable/c/b712da45bd9b9835d132e9fbc0c3e43c164cb1fd"},{"url":"https://git.kernel.org/stable/c/f82a2ded3d7a9098267c84f14eafdb98c4550ac5"},{"url":"https://git.kernel.org/stable/c/b322532a4b774db1b480a2de84125910a70739a5"},{"url":"https://git.kernel.org/stable/c/080695e6f005e2396f1207fd69d24c442cb230c6"}],"tags":["cve.org"],"epss":0.00174,"epssPercentile":0.06506,"ingestedAt":"2026-10-21T12:48:53.579Z","slug":"CVE-2026-74543","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()\n\nsyzbot reported a memory leak [1] in the UDP tunnel NIC offload code.\n\nWhen device registration fails (e.g. in register_netdevice()), netdev core\nunwinds by sending a single NETDEV_UNREGISTER notification. If work was queued\nduring NETDEV_REGISTER (utn->work_pending is set), udp_tunnel_nic_unregister()\nreturns early:\n\n\tif (utn->work_pending)\n\t\treturn;\n\nBecause failed registrations do not enter netdev_wait_allrefs_any(), no\nsubsequent NETDEV_UNREGISTER rebroadcast will ever occur. As a result, the\nstruct udp_tunnel_nic allocated in udp_tunnel_nic_alloc() is leaked\npermanently.\n\nFix this by removing the early return. Instead, synchronously cancel any\npending work with cancel_delayed_work_sync() before freeing @utn.\n\nTo be able to call cancel_delayed_work_sync() while holding RTNL (the work also\nneeds RTNL), switch udp_tunnel_nic_device_sync_work() to rtnl_trylock(). If RTNL\nis contended, requeue the work with a 1 jiffy delay (via queue_delayed_work())\nto prevent high CPU contention while waiting for RTNL lock.\n\nThe utn->work_pending bookkeeping is no longer needed and is removed, as\nthe workqueue core already tracks the pending/running state of the work.\n\n[1]\nBUG: memory leak\nunreferenced object 0xffff888127d5f840 (size 96):\n  comm \"syz-executor\", pid 5806, jiffies 4294942188\n  backtrace (crc 99fdb6c8):\n    __kmalloc_noprof+0x3bf/0x550\n    udp_tunnel_nic_alloc net/ipv4/udp_tunnel_nic.c:756 [inline]\n    udp_tunnel_nic_register net/ipv4/udp_tunnel_nic.c:833 [inline]\n    udp_tunnel_nic_netdevice_event+0x804/0xab0 net/ipv4/udp_tunnel_nic.c:931\n    notifier_call_chain+0x59/0x160 kernel/notifier.c:85\n    call_netdevice_notifiers_info+0x7d/0xb0 net/core/dev.c:2250\n    register_netdevice+0xc10/0xeb0 net/core/dev.c:11478\n\n## Affected\n\n- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < 52c753b46265243406690d980faa9514d3f53827`\n- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < b712da45bd9b9835d132e9fbc0c3e43c164cb1fd`\n- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < f82a2ded3d7a9098267c84f14eafdb98c4550ac5`\n- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < b322532a4b774db1b480a2de84125910a70739a5`\n- `Linux >= cc4e3835eff474aa274d6e1d18f69d9d296d3b76 < 080695e6f005e2396f1207fd69d24c442cb230c6`\n- `Linux 5.9`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}