Out-of-bounds write in libssh2 - CVE-2026-55200
Published: July 1, 2026
Vulnerability identifier: #VU136046
CSH Severity: Critical
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Red
CVE-ID: CVE-2026-55200
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: libssh2.org
Affected software:
libssh2
libssh2
Detailed vulnerability description
The vulnerability allows a remote attacker to compromise vulnerable system.
The vulnerability exists due to a boundary error when processing untrusted input within the ssh2_transport_read() function. A remote attacker can send specially crafted SSH packets with overly long packet_length values, trigger an out-of-bounds write and execute arbitrary code on the target system.
How to mitigate CVE-2026-55200
Install updates from vendor's repository.