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VulnerabilityPublished Updated

CVE-2024-56640: Linux kernel · net/smc: fix LGR and link use-after-free issue

Source GCVE Database

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Not known to be exploited · CVSS 7.8 High.

Data as of 30 Oct 2026, 00:51 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Dec 2024

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: 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 29 Oct 2026.

What to do

AI-suggested

A fix has been implemented that adds sock lock protection to the smc_listen_work() path, preventing concurrent operations from causing reference count underflow. Users should update their Linux kernel to a version that includes this patch once it is released. Until then, no other specific mitigations are indicated.

Description

CVE-2024-56640 is a high-severity use-after-free vulnerability in the Linux kernel's net/smc subsystem. The flaw arises from premature decrement of reference counts (refcnt) on LGR/link objects, leading to unsafe resource access. This occurs due to repeated release of LGR/link refcnt without proper locking, specifically in the server listening path where smc_conn_free() is called multiple times without sock lock protection. The issue has been addressed by adding sock lock protection in the smc_listen_work() path to prevent concurrent connection operations from causing refcount underflow.

References

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