{"affected":[{"conditional":false,"product":"libssh2","source":"NVD","vendor":"libssh2","versions":[{"lessThanOrEqual":"1.11.1","status":"affected","version":"*","versionType":"custom"}]}],"cpeConfigurations":[{"negate":false,"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*","versionEndIncluding":"1.11.1","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"OR"}],"cveId":"CVE-2026-66035","cwes":["CWE-122"],"description":"libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packet_length smaller than the cipher's block size during Encrypt-then-MAC cipher negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit glibc writes attacker-controlled bytes into an adjacent chunk's SIZE field, enabling tcache bin confusion, overlapping live objects, and function pointer overwrite during the session handshake before authentication.","epss":null,"exploits":[],"kev":null,"metrics":[{"score":7.7,"severity":"high","source":"NVD: disclosure@vulncheck.com","vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/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"},{"score":7.5,"severity":"high","source":"NVD: disclosure@vulncheck.com","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}],"modifiedAt":1794168600187,"publishedAt":1784913455547,"references":[{"source":"disclosure@vulncheck.com","tags":["Patch"],"url":"https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4"},{"source":"disclosure@vulncheck.com","tags":["Issue Tracking","Patch"],"url":"https://github.com/libssh2/libssh2/pull/2198"},{"source":"disclosure@vulncheck.com","tags":["Patch","Third Party Advisory"],"url":"https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-cipher-negotiation"}],"remediation":[{"kind":"fix","source":"disclosure@vulncheck.com","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4"},{"kind":"fix","source":"disclosure@vulncheck.com","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://github.com/libssh2/libssh2/pull/2198"},{"kind":"fix","source":"disclosure@vulncheck.com","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-cipher-negotiation"}],"revision":"10d398804c9515498869f18ffddcdab7bcad8ea965b2015f1e81b92d0e687d0c","sources":[{"modifiedAt":1794168600187,"name":"NVD","retrievedAt":1794183359917,"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66035"}],"ssvc":{"assessedAt":1784851200000,"automatable":"no","exploitation":"none","source":"NVD SSVC: 134c704f-9b21-4f2e-91b3-4a467353bcc0","technicalImpact":"total"},"status":"published","title":"CVE-2026-66035","updatedAt":1794183359917}