CVE-2025-21673: smb: client: fix double free of TCP_Server_Info::hostname

mediumCVSS 5.5CVE-2025-21673

CSIRTS triage

vendor: Linux product: Linux kernel Memory corruption

What: A double-free vulnerability in TCP_Server_Info hostname handling affects the SMB client code.
Who is affected: Systems running Linux kernel versions with the vulnerable SMB client code are affected.
Urgency: Remediation is routine; CVSS 5.5 is moderate and no active exploitation reported.
Action: Apply kernel patches that fix the double-free in the SMB client TCP_Server_Info hostname code.

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: medium — CVSS 5.5
Published: 2026-08-06
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21673

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-2025-216730.41% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 34% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2025-21673	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

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