CVE-2026-56766

HighCVSS 8.8

Published: 25/06/2026(UTC)Updated: 14/07/2026(UTC)Translated: 15/07/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Elevated risk

1.33%

68th percentile - higher than 68% of all known CVEs

Summary

A stack buffer overflow vulnerability in Hydra through version 9.7 (fixed in commit 9cc84c2) affects NTLM authentication in SMTP, POP3, IMAP, NNTP, HTTP, HTTP-Proxy, and HTTP-Proxy-Urlenum modules when processing malicious NTLM Type-2 challenges. A remote server can send a crafted 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.

Risk Assessment

An attacker can remotely execute arbitrary code on the vulnerable system, leading to full compromise of the Hydra application and potentially the entire operating system if stack protections are absent.

Recommendation

Immediately update Hydra to a version containing commit 9cc84c2 or later. If an update is not possible, restrict access to services using NTLM (SMTP, POP3, IMAP, NNTP, HTTP, HTTP-Proxy) to trusted servers only.

Other vulnerabilities in Hydra

CVE-2026-68508High
Hydra before version 1.3.4 has an arbitrary code execution vulnerability. The hydra.utils.instantiate() function resolves and calls Python objects selected by configuration, allowing an attacker to invoke dangerous callables.

Original NVD description (English source)

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.