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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.

PUBLISHED Reserved 2026-06-22 | Published 2026-06-25 | Updated 2026-06-25 | Assigner VulnCheck




HIGH: 8.6CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

HIGH: 8.8CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Problem types

Stack-based Buffer Overflow

Product status

Default status
unaffected

Any version
affected

9cc84c20e75f5fef6bb1790bb9ada2afad2204e2 (git)
unaffected

Credits

Tristan Madani finder

References

github.com/...ommit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2 (Patch Commit) patch

www.vulncheck.com/...overflow-in-ntlm-authentication-handler third-party-advisory

cve.org (CVE-2026-56766)

nvd.nist.gov (CVE-2026-56766)

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