CVE-2026-56766 | Hydra through 9.7, fixed in commit 9cc84c2, contains a stack… | CVSS 8.8 HIGH

Description

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.

Metadata

CVE ID: CVE-2026-56766
State: PUBLISHED
Assigner: VulnCheck
Reserved: 2026-06-22 21:55 UTC
Published: 2026-06-25 18:01 UTC
Last updated: 2026-06-25 18:34 UTC
Primary CWE: CWE-121
Stack-based Buffer Overflow
Vendor / Product: vanhauser-thc / thc-hydra
Sources: cve.org · NVD

Severity & Metrics

8.8 HIGH CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

SSVC — CISA Coordinator

Exploitation: none
Automatable: no
Tech. Impact: total

Affected products (1)

Vendor	Product	Platform	Versions
vanhauser-thc	thc-hydra	—	0 ≤ 9.7, 9cc84c20e75f5fef6bb1790bb9ada2afad2204e2

Weakness (CWE)

CWE	Source	Description
CWE-121	cna	Stack-based Buffer Overflow

CVSS scores (2)

Score	Severity	Version	Source	Vector
8.8	HIGH	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.6	HIGH	4.0	cna	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References (2)