CVE-2026-56766: Vanhauser-Thc Thc-Hydra

High severity, CVSS 8.8. EPSS: 2.4% chance of exploitation in the next 30 days.

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.

Affected products

• Vanhauser-Thc Thc-Hydra: up to and including 9.7

Published 2026-06-25. Last modified 2026-07-14.