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VulnerabilityPublished Updated

CVE-2026-72493: Linux kernel · net: serialize netif_running() check in enqueue_to_backlog()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.9 Critical · fixed in cbe10ea090ea9d6fa5ff50c9b44f2a86fe56f0b7 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
9.9Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in cbe10ea090ea9d6fa5ff50c9b44f2a86fe56f0b7, b422e3eff0edf0975de4883929adbed28f9d08bc, 46762cefe7f4e5bffc1eb467810a7bbb02e461d7 +7
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=3.2.71 <3.3
  • >=3.4.111 <3.5
  • >=3.12.48 <3.13
  • >=3.14.54 <3.15
  • >=3.18.22 <3.19
  • >=4.1.9 <4.2
Fixed in
  • cbe10ea090ea9d6fa5ff50c9b44f2a86fe56f0b7
  • b422e3eff0edf0975de4883929adbed28f9d08bc
  • 46762cefe7f4e5bffc1eb467810a7bbb02e461d7
  • 4.2
  • 3.19
  • 3.15
  • 3.13
  • 3.5
  • 3.3
  • 2fface6e0bbd6314d1d9d071abf2c4d67548511c
LinuxLinuxAffected
  • =4.2
Fixed in–

Description

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).

References

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