What is CVE-2026-56766?

CVE-2026-56766 is a high-severity vulnerability in Vanhauser-thc Thc-hydra, classified under Stack-based Buffer Overflow. CVSS score: 8.8/10. Published 2026-06-25.

How severe is CVE-2026-56766?

High severity. CVSS v3 base score is 8.8 out of 10.

Buffer overflow in Vanhauser-thc Thc-hydra

CVE-2026-56766

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 malicio…

Vulnerability class: Buffer Overflow

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Vanhauser-thc Thc-hydra — versions 0, 9cc84c20e75f5fef6bb1790bb9ada2afad2204e2

Weakness classification (CWE)

CWE-121 — Stack-based Buffer Overflow

References

disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-56766?: CVE-2026-56766 is a high-severity vulnerability in Vanhauser-thc Thc-hydra, classified under Stack-based Buffer Overflow. CVSS score: 8.8/10. Published 2026-06-25.
How severe is CVE-2026-56766?: High severity. CVSS v3 base score is 8.8 out of 10.