{"id":"CVE-2026-56766","summary":"Hydra - Stack Buffer Overflow in NTLM Authentication Handler","details":"Hydra through 9.7, fixed in commit 9cc84c2, contains a stack buffer overflow in NTLM authentication across SMTP, POP3, IMAP, NNTP, HTTP, HTTP-Proxy, and HTTP-Proxy-Urlenum modules when processing malicious NTLM Type-2 challenges. A malicious server can send a crafted NTLM Type-2 challenge with an excessively long domain string, causing base64-encoded response data to overflow a 500-byte stack buffer by 18 to 330 bytes, enabling remote code execution on systems without stack protection.","modified":"2026-08-12T16:41:28.806281Z","published":"2026-06-25T18:01:07.362Z","related":["openSUSE-SU-2026:11131-1"],"database_specific":{"cwe_ids":["CWE-121"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56766.json","cna_assigner":"VulnCheck"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56766.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56766"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/hydra-stack-buffer-overflow-in-ntlm-authentication-handler"},{"type":"FIX","url":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2"},{"type":"PACKAGE","url":"https://github.com/vanhauser-thc/thc-hydra"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/vanhauser-thc/thc-hydra","events":[{"introduced":"0"},{"fixed":"6c11ce2dff19ce81630c12b001d821dcd4d1567c"},{"fixed":"9cc84c20e75f5fef6bb1790bb9ada2afad2204e2"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"9.7"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["v9.7","v9.6","v9.5","v9.4","v9.3","v9.2","v9.1","v8.8","v9.0","v8.9.1","8.6","v8.5","v8.4","8.3","v8.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-56766.json","vanir_signatures_modified":"2026-08-12T16:41:28Z","vanir_signatures":[{"deprecated":false,"digest":{"line_hashes":["35448779194819226924972275234383345140","130102629967969958899531356749536731865","231715194860541365935553737987076264770"],"threshold":0.9},"id":"CVE-2026-56766-0c98c52c","signature_type":"Line","signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-imap.c"}},{"deprecated":false,"digest":{"threshold":0.9,"line_hashes":["35448779194819226924972275234383345140","130102629967969958899531356749536731865","231715194860541365935553737987076264770"]},"id":"CVE-2026-56766-1305a1f9","signature_type":"Line","signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-pop3.c"}},{"signature_type":"Line","signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-http.c"},"deprecated":false,"digest":{"line_hashes":["278702205342695463151679248408070047059","126401131644266843577112091998620359097","267152690299679711919951749017107024075"],"threshold":0.9},"id":"CVE-2026-56766-24ef6bb7"},{"target":{"file":"hydra-pop3.c","function":"start_pop3"},"deprecated":false,"digest":{"function_hash":"149535296753010222742306050121223423350","length":7538},"id":"CVE-2026-56766-27a70e75","signature_type":"Function","signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2"},{"deprecated":false,"digest":{"line_hashes":["190992225447068510429261609506372889156","35448779194819226924972275234383345140","130102629967969958899531356749536731865","231715194860541365935553737987076264770"],"threshold":0.9},"id":"CVE-2026-56766-311a4852","signature_type":"Line","signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-smtp.c"}},{"signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-http-proxy-urlenum.c","function":"start_http_proxy_urlenum"},"deprecated":false,"digest":{"function_hash":"137960210208216958018972478822960075752","length":6627},"id":"CVE-2026-56766-5b7f7a6e","signature_type":"Function"},{"id":"CVE-2026-56766-5f34d4c9","signature_type":"Function","signature_version":"v1","source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-smtp.c","function":"start_smtp"},"deprecated":false,"digest":{"function_hash":"337775584107080223284065532835179464867","length":6056}},{"source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-nntp.c","function":"start_nntp"},"deprecated":false,"digest":{"length":5983,"function_hash":"77233272943885351528390861051041917127"},"id":"CVE-2026-56766-7e7e4b04","signature_type":"Function","signature_version":"v1"},{"source":"https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2","target":{"file":"hydra-http.c","function":"start_http"},"deprecated":false,"digest":{"function_hash":"146931814249048069120793061934488840833","length":8242},"id":"CVE-2026-56766-8f77bc95","signature_type":"Function","signature_version":"v1"},{"target":{"file":"hydra-http-proxy.c"},"deprecated":false,"digest":{"threshold":0.9,"line_hashes":["14131935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