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net: serialize netif_running() check in enqueue_to_backlog()

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: net: serialize netif_running() check in enqueue_to_backlog() Syzbot reported a KASAN slab-use-after-free in fib_rules_lookup(). The root cause is a race condition where packets can escape the backlog flushing during device unregistration (e.g., during netns exit). Commit e9e4dd3267d0 ("net: do not process device backlog during unregistration") introduced a lockless netif_running() check in enqueue_to_backlog() to prevent queuing packets to an unregistering device. However, this creates a TOCTOU race window. A lockless transmitter (like veth_xmit) can pass the check before dev_close() clears IFF_UP. If the transmitter is then delayed, flush_all_backlogs() can run and finish before the transmitter grabs the backlog lock and queues the packet. The packet then escapes the flush and triggers UAF later when processed. Fix this by moving the netif_running() check inside the backlog lock. This serializes the check with the flush work (which also grabs the lock). We then either queue the packet before the flush runs (so it gets flushed), or check netif_running() after the flush/close completes (so it gets dropped).

Announced Source revision 1
Original source ↗

CVE-2026-72493

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-72493

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "e9e4dd3267d0c5234c5c0f47440456b10875dec9",
        "lessThan": "cbe10ea090ea9d6fa5ff50c9b44f2a86fe56f0b7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e9e4dd3267d0c5234c5c0f47440456b10875dec9",
        "lessThan": "b422e3eff0edf0975de4883929adbed28f9d08bc",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e9e4dd3267d0c5234c5c0f47440456b10875dec9",
        "lessThan": "2fface6e0bbd6314d1d9d071abf2c4d67548511c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e9e4dd3267d0c5234c5c0f47440456b10875dec9",
        "lessThan": "46762cefe7f4e5bffc1eb467810a7bbb02e461d7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "78b6803a1961369d0b8350ff1f99b7375bbd7a8f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b5d73d9cdd6be22795499890ea928a6f57ef829c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f6533fed1bfa842e391ee50f9a9c5e963c71e579",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "2095ab2456da766174cda8bc105d7a7b1bc70e16",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f1fdb184aefa8447560e3ea0e605171592ffee41",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f75c8a3015422128ca150e81c730bc2a471b5f4a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3.2.71",
        "lessThan": "3.3",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "3.4.111",
        "lessThan": "3.5",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "3.12.48",
        "lessThan": "3.13",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "3.14.54",
        "lessThan": "3.15",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "3.18.22",
        "lessThan": "3.19",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "4.1.9",
        "lessThan": "4.2",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "net/core/dev.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.2"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.2",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.12.114",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.57",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.1.5",
        "versionType": "semver",
        "lessThanOrEqual": "7.1.*"
      },
      {
        "status": "unaffected",
        "version": "7.2",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/core/dev.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-72493

Source reference: /cveMetadata/cveId

Publisher severity

critical

Source reference: /containers/cna/metrics

Event
#46527 · Revision 1
Added to Heist Feed
Publisher date
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