{"id":"CVE-2026-66034","aliases":[],"url":"https://o3.security/vulnerability/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.","published":"2026-07-24T16:42:18.764Z","modified":"2026-08-27T18:26:18.003991121Z","cvss":null,"epss":{"score":0.00402,"percentile":0.33557,"asOf":"2026-09-08"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[],"fix":{"url":"https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9","label":"libssh2/libssh2@a13bb6c"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T18:26:18.003991121Z"}}