{"id":"JLSEC-2026-1088","summary":"libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer...","details":"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.","modified":"2026-07-31T18:20:49.821118906Z","published":"2026-07-31T18:09:08.751Z","upstream":["CVE-2026-66035","EUVD-2026-48722","GHSA-v6rf-8q4r-r495"],"database_specific":{"license":"CC-BY-4.0","sources":[{"database_specific":{"status":"Analyzed"},"id":"CVE-2026-66035","imported":"2026-07-31T17:07:21.975Z","modified":"2026-07-30T15:41:05.690Z","published":"2026-07-24T17:17:35.547Z","url":"https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-66035","html_url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66035"},{"modified":"2026-07-24T18:31:41Z","published":"2026-07-24T18:31:30Z","url":"https://api.github.com/advisories/GHSA-v6rf-8q4r-r495","html_url":"https://github.com/advisories/GHSA-v6rf-8q4r-r495","id":"GHSA-v6rf-8q4r-r495","imported":"2026-07-31T17:07:26.589Z"},{"imported":"2026-07-31T17:07:23.798Z","modified":"2026-07-28T01:06:26Z","published":"2026-07-24T16:45:24Z","url":"https://euvdservices.enisa.europa.eu/api/enisaid?id=EUVD-2026-48722","html_url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-48722","id":"EUVD-2026-48722"}]},"references":[{"type":"WEB","url":"https://github.com/advisories/GHSA-v6rf-8q4r-r495"},{"type":"WEB","url":"https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4"},{"type":"WEB","url":"https://github.com/libssh2/libssh2/pull/2198"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66035"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-cipher-negotiation"}],"affected":[{"package":{"name":"LibSSH2_jll","ecosystem":"Julia","purl":"pkg:julia/LibSSH2_jll?uuid=29816b5a-b9ab-546f-933c-edad1886dfa8"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.11.104+0"}]}],"database_specific":{"source":"https://github.com/JuliaLang/SecurityAdvisories.jl/tree/generated/osv/2026/JLSEC-2026-1088.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"},{"type":"CVSS_V4","score":"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"}]}