DSA-6365-1 libssh2 - security update

unknownCVE-2025-15661 CVE-2026-7598 CVE-2026-55199 CVE-2026-55200

Multiple security vulnerabilities were discovered in libssh2, a client-side C library implementing the SSH2 protocol which could result in memory disclosure, denial of service or potentially the execution of arbitrary code. https://security-tracker.debian.org/tracker/DSA-6365-1

CSIRTS triage

vendor: libssh2 product: libssh2 Memory corruption Denial of service Remote code execution

What: Multiple security vulnerabilities could result in memory disclosure, denial of service, or potentially the execution of arbitrary code.
Who is affected: Deployments of libssh2 are affected.
Urgency: Remediation is urgent due to the potential for arbitrary code execution.
Action: Update to the latest version of libssh2.

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

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Details

Source: Debian Security Advisories (INTL · vendor-psirt · site)
Severity: unknown
Published: 2026-06-25
Exploitation: Not in CISA KEV at last sync

Original advisory: https://lists.debian.org/debian-security-announce/2026/msg00276.html

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-2025-156610.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 18% of all scored CVEs.
Low exploitation riskCVE-2026-75980.47% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 37% of all scored CVEs.
Low exploitation riskCVE-2026-551990.41% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 33% of all scored CVEs.
Low exploitation riskCVE-2026-552000.73% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 50% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2025-15661	coverage & exploitation status	NVD · CVE.org
CVE-2026-7598	coverage & exploitation status	NVD · CVE.org
CVE-2026-55199	coverage & exploitation status	NVD · CVE.org
CVE-2026-55200	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

unknownMultiple vulnerabilities in Microsoft Azure Linux (July 7, 2026)cert-fr-avis
high[UPDATE] [high] libssh2: Multiple vulnerabilitiescert-bund
unknownNCSC-2026-0210 [1.01] [M/H] Vulnerabilities fixed in libssh2 by libsshncsc-nl
mediumCVE-2026-55199: libssh2 - Pre-Authentication DoS via SSH_MSG_EXT_INFO Handlermsrc
highCVE-2026-55200: libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.cmsrc
mediumCVE-2025-15661: libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.cmsrc