CVE-2026-56766 Hydra - Stack Buffer Overflow in NTLM Authentication Handler
A malicious server can trigger a stack buffer overflow in Hydra's NTLM handler, potentially allowing remote code execution on the client system.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-56766?
CVE-2026-56766 is a high-severity memory corruption vulnerability in vanhauser-thc thc-hydra, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-121
Which versions are affected by CVE-2026-56766?
Linux distribution packages (1)
hydra openSUSE:Tumbleweed | All versions | 9.7+git20.gbccaea1-1.1 |
How do I fix CVE-2026-56766?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-56766 being exploited?
There is no known exploitation of CVE-2026-56766 in the wild and no public exploit code.
Public exploit code: 1 Exploit-DB entry.
Sources
Also known as GHSA-3r6x-6cp5-6575, UBUNTU-CVE-2026-56766, openSUSE-SU-2026:11131-1.