CVE-2026-59850: Libssh: libssh: use-after-free via data callbacks on closed channels

mediumCVSS 4.3CVE-2026-59850

CSIRTS triage

vendor: Libssh product: libsshOther

What: A use-after-free vulnerability occurs via data callbacks on closed channels.
Who is affected: Users of libssh are affected by this vulnerability.
Urgency: Remediation is medium urgency due to the medium severity of the vulnerability.
Action: Update to a patched version of libssh.

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 4.3
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59850

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-2026-598500.30% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 23% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-59850	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

Recent advisories for Libssh

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.

high[NEW] [high] libssh: Multiple vulnerabilitiescert-bund · 2026-07-30
medium[UPDATE] [medium] libssh: Vulnerability allows Denial of Servicecert-bund · 2026-07-28
highCVE-2026-59851: A flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path d…nvd · 2026-07-21
mediumCVE-2026-59850: A flaw was found in libssh. If data packets are processed after a channel is closed, channel d…nvd · 2026-07-21
lowCVE-2026-59849: A flaw was found in libssh. Logic errors in automatic certificate-based public key authenticat…nvd · 2026-07-21
mediumCVE-2026-59848: A flaw was found in libssh. A malicious SFTP server can send responses for unknown request IDs…nvd · 2026-07-21