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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction Active

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction Required

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable no

Technical Impact total

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
vanhauser-thc thc-hydra unaffected
Version Status Constraints
0 affected ≤ 9.7
9cc84c20e75f5fef6bb1790bb9ada2afad2204e2 unaffected —

No data.

No data.

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2 cve-icon
https://www.vulncheck.com/advisories/hydra-stack-buffer-overflow-in-ntlm-authentication-handler cve-icon
History

Fri, 26 Jun 2026 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Vanhauser-thc
Vanhauser-thc thc-hydra
Vendors & Products Vanhauser-thc
Vanhauser-thc thc-hydra

Thu, 25 Jun 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Thu, 25 Jun 2026 18:30:00 +0000

Type Values Removed Values Added
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.
Title Hydra - Stack Buffer Overflow in NTLM Authentication Handler
Weaknesses CWE-121
References
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 8.6, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-06-25T18:34:53.467Z

Reserved: 2026-06-22T21:55:17.942Z

Link: CVE-2026-56766

cve-icon Vulnrichment

Updated: 2026-06-25T18:34:29.403Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-26T09:36:45Z

Weaknesses