{"id":"CVE-2026-55200","state":"PUBLISHED","title":"libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c","description":"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.","publishedAt":"2026-06-17T19:03:15.183Z","updatedAt":"2026-10-22T18:33:35.066Z","severity":{"score":9.2,"label":"Critical","version":"4.0","vector":"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","source":"VulnCheck"},"assigner":"VulnCheck","products":["libssh2 libssh2"],"affected":[{"vendor":"libssh2","product":"libssh2","packageURL":"pkg:github/libssh2/libssh2","defaultStatus":"unaffected","versions":[{"version":"1.11.1","status":"affected","versionType":"semver"},{"version":"1c3f1b7da588f2652260285529ec3c1f1125eb4e","status":"affected","lessThan":"97acf3dfda80c91c3a8c9f2372546301d4a1a7a8","versionType":"git"}],"repo":"https://github.com/libssh2/libssh2"}],"references":["https://github.com/libssh2/libssh2/pull/2052","https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8","https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c","https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc"],"weaknesses":["CWE-680"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/55xxx/CVE-2026-55200.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55200","state":"PUBLISHED","datePublished":"2026-06-17T19:03:15.183Z","dateUpdated":"2026-10-22T18:33:35.066Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-06-16T15:53:37.764Z"},"containers":{"cna":{"title":"libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"libssh2","product":"libssh2","packageURL":"pkg:github/libssh2/libssh2","defaultStatus":"unaffected","versions":[{"version":"1.11.1","status":"affected","versionType":"semver"},{"version":"1c3f1b7da588f2652260285529ec3c1f1125eb4e","status":"affected","lessThan":"97acf3dfda80c91c3a8c9f2372546301d4a1a7a8","versionType":"git"}],"repo":"https://github.com/libssh2/libssh2"}],"references":[{"url":"https://github.com/libssh2/libssh2/pull/2052","name":"Pull Request","tags":["issue-tracking"]},{"url":"https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8","name":"Patch Commit","tags":["patch"]},{"url":"https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"CRITICAL","baseScore":9.2,"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"}},{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH","version":"3.1","baseSeverity":"HIGH","baseScore":8.1,"vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-680","lang":"en","description":"Integer Overflow to Buffer Overflow","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-10-22T18:33:35.066Z"},"tags":["x_open-source"],"datePublic":"2026-06-12T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*","versionStartIncluding":"1.11.1"}]}]}],"credits":[{"lang":"en","value":"Tristan Madani (@TristanInSec)","type":"finder"}],"x_generator":{"engine":"vulncheck"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-06-17T00:00:00+00:00","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3","id":"CVE-2026-55200"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-01T03:55:44.592Z"}}]}}}