CVE-2026-56766

EUVD-2026-39515

25.06.2026, 19:16

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.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	Primary	8.8 HIGH	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Awaiting analysis

This vulnerability is currently awaiting analysis.

Base Score

CVSS 3.x

EPSS Score

Percentile: Unknown

Common Weakness Enumeration

CWE-121 - Stack-based Buffer Overflow
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

References

https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2

https://www.vulncheck.com/advisories/hydra-stack-buffer-overflow-in-ntlm-authentication-handler