{"cvss":9.2,"datePublished":"2026-06-17T20:17:28.667","dateUpdated":"2026-10-22T19:17:55.937","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.","id":"CVE-2026-55200","raw":{"affected":[{"affectedData":[{"defaultStatus":"unaffected","packageURL":"pkg:github/libssh2/libssh2","product":"libssh2","repo":"https://github.com/libssh2/libssh2","vendor":"libssh2","versions":[{"status":"affected","version":"1.11.1","versionType":"semver"},{"lessThan":"97acf3dfda80c91c3a8c9f2372546301d4a1a7a8","status":"affected","version":"1c3f1b7da588f2652260285529ec3c1f1125eb4e","versionType":"git"}]}],"source":"disclosure@vulncheck.com"}],"configurations":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:libssh2:libssh2:1.11.1:*:*:*:*:*:*:*","matchCriteriaId":"B190FBC9-6216-4759-BEF0-747B01BBD92B","vulnerable":true}],"negate":false,"operator":"OR"}]}],"cveTags":[],"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."}],"id":"CVE-2026-55200","lastModified":"2026-10-22T19:17:55.937","metrics":{"cvssMetricV31":[{"cvssData":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.1,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"exploitabilityScore":2.2,"impactScore":5.9,"source":"disclosure@vulncheck.com","type":"Secondary"},{"cvssData":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":8.3,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L","version":"3.1"},"exploitabilityScore":2.8,"impactScore":5.5,"source":"nvd@nist.gov","type":"Primary"}],"cvssMetricV40":[{"cvssData":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","availabilityRequirement":"NOT_DEFINED","baseScore":9.2,"baseSeverity":"CRITICAL","confidentialityRequirement":"NOT_DEFINED","exploitMaturity":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnerabilityResponseEffort":"NOT_DEFINED"},"source":"disclosure@vulncheck.com","type":"Secondary"}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"id":"CVE-2026-55200","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","timestamp":"2026-06-17T00:00:00+00:00","version":"2.0.3"}}]},"published":"2026-06-17T20:17:28.667","references":[{"source":"disclosure@vulncheck.com","tags":["Patch"],"url":"https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8"},{"source":"disclosure@vulncheck.com","tags":["Patch"],"url":"https://github.com/libssh2/libssh2/pull/2052"},{"source":"disclosure@vulncheck.com","tags":["Third Party Advisory"],"url":"https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c"},{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":["Exploit","Third Party Advisory"],"url":"https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc"}],"sourceIdentifier":"disclosure@vulncheck.com","vulnStatus":"Modified","weaknesses":[{"description":[{"lang":"en","value":"CWE-680"}],"source":"disclosure@vulncheck.com","type":"Secondary"}]},"severity":"CRITICAL","source":"nvd","title":"libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that ..."}