{"id":"CVE-2026-74543","state":"PUBLISHED","title":"net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()","description":"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 (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","publishedAt":"2026-08-15T12:27:53.336Z","updatedAt":"2026-10-30T12:30:08.864Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"d53a8b927ac9788257266e115d4901ec6f455387","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"52c753b46265243406690d980faa9514d3f53827","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"b712da45bd9b9835d132e9fbc0c3e43c164cb1fd","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"f82a2ded3d7a9098267c84f14eafdb98c4550ac5","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"b322532a4b774db1b480a2de84125910a70739a5","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"080695e6f005e2396f1207fd69d24c442cb230c6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/udp_tunnel_nic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.9","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.103","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.44","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.8","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/udp_tunnel_nic.c"]}],"references":["https://git.kernel.org/stable/c/d53a8b927ac9788257266e115d4901ec6f455387","https://git.kernel.org/stable/c/52c753b46265243406690d980faa9514d3f53827","https://git.kernel.org/stable/c/b712da45bd9b9835d132e9fbc0c3e43c164cb1fd","https://git.kernel.org/stable/c/f82a2ded3d7a9098267c84f14eafdb98c4550ac5","https://git.kernel.org/stable/c/b322532a4b774db1b480a2de84125910a70739a5","https://git.kernel.org/stable/c/080695e6f005e2396f1207fd69d24c442cb230c6"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74543.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74543","state":"PUBLISHED","datePublished":"2026-08-15T12:27:53.336Z","dateUpdated":"2026-10-30T12:30:08.864Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.914Z"},"containers":{"cna":{"title":"net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()","descriptions":[{"lang":"en","value":"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 (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"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"d53a8b927ac9788257266e115d4901ec6f455387","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"52c753b46265243406690d980faa9514d3f53827","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"b712da45bd9b9835d132e9fbc0c3e43c164cb1fd","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"f82a2ded3d7a9098267c84f14eafdb98c4550ac5","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"b322532a4b774db1b480a2de84125910a70739a5","versionType":"git"},{"version":"cc4e3835eff474aa274d6e1d18f69d9d296d3b76","status":"affected","lessThan":"080695e6f005e2396f1207fd69d24c442cb230c6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/udp_tunnel_nic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.9","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.103","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.44","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.8","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/udp_tunnel_nic.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d53a8b927ac9788257266e115d4901ec6f455387"},{"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"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:30:08.864Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.12.103"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.18.44"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"7.1.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}