Published Jun 17, 2026Sources checked Nov 12, 2026
8.3HIGHCVSS out of 10
What this means
Review the available evidence
CVE-2026-55200 and is rated High severity with a CVSS score of 8.3. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.
What to do next
Remediation and response
Microsoft Security Response Center guidance
Vendor revision: Jul 3, 2026
CBL-Mariner Releases
Vendor-listed releases
1.11.1-3
CISA KEVNot listedBased on the latest collected catalog
EPSS3.9%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2026-55200?
libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.