CVE-2026-55200: libssh2 memory corruption with possible RCE

libssh2 through 1.11.1, fixed in commit 7acf3df 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. References

    https://nvd.nist.gov/vuln/detail/CVE-2026-55200
    libssh2/libssh2#2052
    libssh2/libssh2@97acf3d
    https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c
    https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc
    https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc