{"id":"CVE-2026-66034","summary":"libssh2 Heap Out-of-Bounds Read via publickey subsystem","details":"libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.","modified":"2026-07-28T04:03:11.784535760Z","published":"2026-07-24T16:42:18.764Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-125","CWE-908"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66034.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66034.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66034"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/libssh2-heap-out-of-bounds-read-via-publickey-subsystem"},{"type":"FIX","url":"https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9"},{"type":"FIX","url":"https://github.com/libssh2/libssh2/pull/2202"},{"type":"PACKAGE","url":"https://github.com/libssh2/libssh2"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/libssh2/libssh2","events":[{"introduced":"9896c291e46787352151daa0fabf8be81d84cd09"},{"fixed":"a312b43325e3383c865a87bb1d26cb52e3292641"},{"fixed":"a13bb6c773f0d55ad1628cede57e99803cd898d9"}],"database_specific":{"extracted_events":[{"introduced":"libssh2"},{"fixed":"1.11.1"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["libssh2-1.11.1","libssh2-1.11.0","libssh2-1.10.0","libssh2-1.9.0","libssh2-1.8.0","libssh2-1.7.0","libssh2-1.6.0","libssh2-1.5.0","libssh2-1.4.3","libssh2-1.4.2","libssh2-1.4.1","libssh2-1.4.0","libssh2-1.3.0","libssh2-1.2.9","libssh2-1.2.8","libssh2-1.2.7","libssh2-1.2.6","libssh2-1.2.5","libssh2-1.2.4","libssh2-1.2.3","libssh2-1.2.1","libssh2-1.2","RELEASE.1.1","RELEASE.1.0","RELEASE.0.18","RELEASE.0.17","RELEASE.0.16","RELEASE.0.15","beforenb2-0.14"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-66034.json"}}],"schema_version":"1.7.5","severity":[{"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"}]}