CVE-2024-56640: Linux kernel · net/smc: fix LGR and link use-after-free issue
Source GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 30 Oct 2026, 00:51 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Dec 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
- nvd.nist.gov/vuln/detail/CVE-2024-56640 (opens in a new tab)
- git.kernel.org/stable/c/0cf598548a6c36d90681d53c6b77d52363f2f295 (opens in a new tab)
- git.kernel.org/stable/c/2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7 (opens in a new tab)
- git.kernel.org/stable/c/673d606683ac70bc074ca6676b938bff18635226 (opens in a new tab)
- git.kernel.org/stable/c/6f0ae06a234a78ae137064f2c89135ac078a00eb (opens in a new tab)
- git.kernel.org/stable/c/f502a88fdd415647a1f2dc45fac71b9c522a052b (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/03/msg00001.html (opens in a new tab)