[UPDATE] [high] libssh2: Multiple vulnerabilities
A remote, anonymous attacker can exploit multiple vulnerabilities in libssh2 to conduct a denial of service attack or execute code.
CSIRTS triage
- What
- Multiple vulnerabilities in libssh2 can lead to denial of service or code execution.
- Who is affected
- Deployments of libssh2 are affected.
- Urgency
- Remediation is high urgency due to the potential for exploitation and high severity.
- Action
- Apply patches as soon as they are available.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-1996
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.
- Moderate exploitation riskCVE-2026-552004.0% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 90% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-551990.92% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 58% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-55200 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-55199 | 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
- unknownDSA-6365-1 libssh2 - security updatedebian
- 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
Recent advisories for libssh2
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.
- medium[UPDATE] [mittel] libssh2: Schwachstelle ermöglicht Denial of Servicecert-bund · 2026-09-07
- high[UPDATE] [hoch] libssh2: Mehrere Schwachstellencert-bund · 2026-09-07
- medium[UPDATE] [mittel] libssh2: Mehrere Schwachstellencert-bund · 2026-09-07
- medium[UPDATE] [mittel] libssh2: Schwachstelle ermöglicht Denial of Service und Offenlegung von Informationencert-bund · 2026-09-07
- unknownUSN-8722-1: libssh2 vulnerabilitiesubuntu · 2026-09-03
- criticalCVE-2026-5917: libgit2 versions v0.27.0 through v1.9.0 built with the libssh2 SSH backend (USE_SSH=libssh2) co…nvd · 2026-08-11
More from CERT-Bund (BSI) Security Advisories
- high[UPDATE] [hoch] Red Hat Enterprise Linux (postgis, virtuoso-opensource): Mehrere Schwachstellen2026-09-11
- medium[UPDATE] [mittel] Red Hat Enterprise Linux: Mehrere Schwachstellen2026-09-11
- medium[UPDATE] [mittel] Linux Kernel: Schwachstelle ermöglicht Denial of Service2026-09-11
- medium[UPDATE] [mittel] Linux Kernel: Mehrere Schwachstellen2026-09-11
- high[UPDATE] [hoch] OpenSSL: Mehrere Schwachstellen2026-09-11