CVE-2025-40139: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().

highCVSS 8.4CVE-2025-40139

CSIRTS triage

vendor: Linux product: Linux Kernel Memory corruption

What: Use-after-free or race condition in SMC protocol CLC prefix setting due to missing socket destination reference handling.
Who is affected: Linux systems with SMC (Shared Memory Communications) protocol support enabled and in use.
Urgency: High priority; CVSS 8.4 severity and potential for kernel crash or code execution.
Action: Apply kernel update using proper __sk_dst_get() and dst_dev_rcu() locking in smc_clc_prfx_set().

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 8.4
Published: 2026-08-06
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-40139

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2025-401390.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2025-40139	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[UPDATE] [high] Linux Kernel: Multiple vulnerabilitiescert-bund

Recent advisories for smc

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownCVE-2026-74719: In the Linux kernel, the following vulnerability has been resolved: net/smc: fix qentry overwr…nvd · 2026-08-22
highCVE-2026-74692: In the Linux kernel, the following vulnerability has been resolved: net/smc: fix TOCTOU race b…nvd · 2026-08-22
highCVE-2026-74631: In the Linux kernel, the following vulnerability has been resolved: net: smc: fix splice entry…nvd · 2026-08-22
criticalCVE-2026-74493: In the Linux kernel, the following vulnerability has been resolved: net/smc: fix socket use-af…nvd · 2026-08-15
mediumCVE-2026-74631: net: smc: fix splice entry lifetime imbalance in smc_rx_splicemsrc · 2026-08-11
mediumCVE-2026-74692: net/smc: fix TOCTOU race between smc_listen_out() and listener closemsrc · 2026-08-11