CVE-2026-56766CWE-121

Hydra - Stack Buffer Overflow in NTLM Authentication Handler

High · published June 25, 2026

CVSS v4.0
8.6
EPSS
2%
Percentile
84.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
8.6 · HIGH
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
EPSS
0.02438 · 84.2th percentile
Weakness
CWE-121 · Stack-based Buffer Overflow
Published
2026-06-25T18:01Z
EPSS history
Timeline
  • 25 JUN 18:01Z
    Hydra - Stack Buffer Overflow in NTLM Authentication Handler
    cvelistv5