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CVE-2026-74543 (GCVE-0-2026-74543)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:27 – Updated: 2026-08-17 05:21
VLAI
Title
net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()
Summary
In the Linux kernel, the following vulnerability has been resolved: net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister() syzbot reported a memory leak [1] in the UDP tunnel NIC offload code. When device registration fails (e.g. in register_netdevice()), netdev core unwinds by sending a single NETDEV_UNREGISTER notification. If work was queued during NETDEV_REGISTER (utn->work_pending is set), udp_tunnel_nic_unregister() returns early: if (utn->work_pending) return; Because failed registrations do not enter netdev_wait_allrefs_any(), no subsequent NETDEV_UNREGISTER rebroadcast will ever occur. As a result, the struct udp_tunnel_nic allocated in udp_tunnel_nic_alloc() is leaked permanently. Fix this by removing the early return. Instead, synchronously cancel any pending work with cancel_delayed_work_sync() before freeing @utn. To be able to call cancel_delayed_work_sync() while holding RTNL (the work also needs RTNL), switch udp_tunnel_nic_device_sync_work() to rtnl_trylock(). If RTNL is contended, requeue the work with a 1 jiffy delay (via queue_delayed_work()) to prevent high CPU contention while waiting for RTNL lock. The utn->work_pending bookkeeping is no longer needed and is removed, as the workqueue core already tracks the pending/running state of the work. [1] BUG: memory leak unreferenced object 0xffff888127d5f840 (size 96): comm "syz-executor", pid 5806, jiffies 4294942188 backtrace (crc 99fdb6c8): __kmalloc_noprof+0x3bf/0x550 udp_tunnel_nic_alloc net/ipv4/udp_tunnel_nic.c:756 [inline] udp_tunnel_nic_register net/ipv4/udp_tunnel_nic.c:833 [inline] udp_tunnel_nic_netdevice_event+0x804/0xab0 net/ipv4/udp_tunnel_nic.c:931 notifier_call_chain+0x59/0x160 kernel/notifier.c:85 call_netdevice_notifiers_info+0x7d/0xb0 net/core/dev.c:2250 register_netdevice+0xc10/0xeb0 net/core/dev.c:11478
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: cc4e3835eff474aa274d6e1d18f69d9d296d3b76 , < b712da45bd9b9835d132e9fbc0c3e43c164cb1fd (git)
Affected: cc4e3835eff474aa274d6e1d18f69d9d296d3b76 , < f82a2ded3d7a9098267c84f14eafdb98c4550ac5 (git)
Affected: cc4e3835eff474aa274d6e1d18f69d9d296d3b76 , < b322532a4b774db1b480a2de84125910a70739a5 (git)
Affected: cc4e3835eff474aa274d6e1d18f69d9d296d3b76 , < 080695e6f005e2396f1207fd69d24c442cb230c6 (git)
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Linux Linux Affected: 5.9
Unaffected: 0 , < 5.9 (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/udp_tunnel_nic.c"
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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      "cpeApplicability": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.103",
                  "versionStartIncluding": "5.9",
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
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          "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-\u003ework_pending is set), udp_tunnel_nic_unregister()\nreturns early:\n\n\tif (utn-\u003ework_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-\u003ework_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"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:21:28.314Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "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"
        }
      ],
      "title": "net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74543",
    "datePublished": "2026-08-15T12:27:53.336Z",
    "dateReserved": "2026-08-15T05:44:03.914Z",
    "dateUpdated": "2026-08-17T05:21:28.314Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74543",
      "date": "2026-09-04",
      "epss": "0.00168",
      "percentile": "0.06395"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-74543\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-15T13:17:59.643\",\"lastModified\":\"2026-08-17T06:19:51.503\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"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-\u003ework_pending is set), udp_tunnel_nic_unregister()\\nreturns early:\\n\\n\\tif (utn-\u003ework_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-\u003ework_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\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/ipv4/udp_tunnel_nic.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"cc4e3835eff474aa274d6e1d18f69d9d296d3b76\",\"lessThan\":\"b712da45bd9b9835d132e9fbc0c3e43c164cb1fd\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cc4e3835eff474aa274d6e1d18f69d9d296d3b76\",\"lessThan\":\"f82a2ded3d7a9098267c84f14eafdb98c4550ac5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cc4e3835eff474aa274d6e1d18f69d9d296d3b76\",\"lessThan\":\"b322532a4b774db1b480a2de84125910a70739a5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cc4e3835eff474aa274d6e1d18f69d9d296d3b76\",\"lessThan\":\"080695e6f005e2396f1207fd69d24c442cb230c6\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/ipv4/udp_tunnel_nic.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.9\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.9\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.103\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.44\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.8\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/080695e6f005e2396f1207fd69d24c442cb230c6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b322532a4b774db1b480a2de84125910a70739a5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b712da45bd9b9835d132e9fbc0c3e43c164cb1fd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f82a2ded3d7a9098267c84f14eafdb98c4550ac5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-21T08:56:13+00:00",
      "cve": "CVE-2026-74543",
      "id": "CVE-2026-74543",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: udp_tunnel: fix memory leak in udp_tunnel_nic_unregister()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74543.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.