CVE-2026-56766 Details
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.
A stack buffer overflow vulnerability has been identified in Hydra versions through 9.7, fixed in commit 9cc84c2. The issue arises in the NTLM authentication process across several modules, including SMTP, POP3, IMAP, NNTP, HTTP, HTTP-Proxy, and HTTP-Proxy-Urlenum. The vulnerability is triggered when the application processes malicious NTLM Type-2 challenges. A crafted challenge from a malicious server can exploit this flaw by sending an excessively long domain string, causing the base64-encoded response to overflow a 500-byte stack buffer by 18 to 330 bytes. This overflow can lead to remote code execution on systems lacking stack protection.
Users can update to Hydra version 9.8 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jun 25, 2026CISA-ADP
Assessed Jun 25, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-121 | Stack-based Buffer Overflow | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Hydra | <= 9.7 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 14, 2026 | CVE Modified | [email protected] |
| Jun 25, 2026 | New CVE Received | [email protected] |
| Jun 25, 2026 | CVE Modified | CISA-ADP |