{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-55200: libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-55200","status":"final","version":"1","initial_release_date":"2026-06-17T19:03:15.183Z","current_release_date":"2026-06-17T19:45:11.371Z","revision_history":[{"date":"2026-06-17T19:03:15.183Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"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.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-55200 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-55200"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-55200"},{"category":"external","summary":"Pull Request","url":"https://github.com/libssh2/libssh2/pull/2052"},{"category":"external","summary":"Patch Commit","url":"https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8"},{"category":"external","summary":"vulncheck.com","url":"https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c"}]},"product_tree":{"branches":[{"category":"vendor","name":"libssh2","branches":[{"category":"product_name","name":"libssh2","branches":[{"category":"product_version_range","name":"<=1.11.1","product":{"name":"libssh2 libssh2 <=1.11.1","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"7acf3dfda80c91c3a8c9f2372546301d4a1a7a8","product":{"name":"libssh2 libssh2 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8","product_id":"CSAFPID-2","product_identification_helper":{"cpe":"cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-55200","title":"libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c","notes":[{"category":"description","text":"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.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1"],"fixed":["CSAFPID-2"]},"scores":[{"cvss_v4":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","baseScore":9.2,"baseSeverity":"CRITICAL"},"products":["CSAFPID-1"]}],"remediations":[{"category":"vendor_fix","details":"Update to a fixed version: 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8.","product_ids":["CSAFPID-1"],"url":"https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8"}]}]}