CVE-2026-55200: libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c
CSIRTS triage
- What
- There is an out-of-bounds write vulnerability due to unchecked packet length in transport.c.
- Who is affected
- Deployments of libssh2 are affected.
- Urgency
- Remediation is urgent due to the high severity and potential for exploitation.
- 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
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55200
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-2026-552002.0% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 79% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| 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.
- high[UPDATE] [high] libssh2: Multiple vulnerabilitiescert-bund
- unknownDSA-6365-1 libssh2 - security updatedebian
- unknownNCSC-2026-0210 [1.01] [M/H] Vulnerabilities fixed in libssh2 by libsshncsc-nl
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