CVE-2026-56766

HIGHPre-NVD 8.88.8—
EchelonGraph scoreHIGH confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-06-25. a secondary CVSS source baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
8.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
8.8
EG Score
8.8(high)
EPSS
37.6%
KEV
Not listed

Published

June 25, 2026

Last Modified

June 25, 2026

Advisory Details (2)

Auto-updated Jun 25, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic

Hydra - Stack Buffer Overflow in NTLM Authentication Handler | Advisories | VulnCheck

https://www.vulncheck.com/advisories/hydra-stack-buffer-overflow-in-ntlm-authentication-handler
github_commit

commit 9cc84c20e75f (vanhauser-thc/thc-hydra)

Fix landed in vanhauser-thc/thc-hydra commit 9cc84c20e75f — awaiting tagged release

https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2

Vendor Advisories for CVE-2026-56766(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 36× in last 7d / 57× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 20:09 UTCEG score recompute
  2. 2026-07-06 20:09 UTCGHSA enrichment
  3. 2026-07-06 16:27 UTCEPSS rescore
  4. 2026-07-06 16:27 UTCEPSS rescore
  5. 2026-07-06 06:59 UTCEG score recompute
  6. 2026-07-06 06:59 UTCGHSA enrichment
  7. 2026-07-06 02:23 UTCEPSS rescore
  8. 2026-07-06 02:23 UTCEPSS rescore
  9. 2026-07-05 17:54 UTCEG score recompute
  10. 2026-07-05 17:54 UTCGHSA enrichment
  11. 2026-07-05 04:49 UTCEG score recompute
  12. 2026-07-05 04:49 UTCGHSA enrichment
  13. 2026-07-05 02:31 UTCEPSS rescore
  14. 2026-07-05 02:30 UTCEPSS rescore
  15. 2026-07-04 15:29 UTCEG score recompute
  16. 2026-07-04 15:29 UTCGHSA enrichment
  17. 2026-07-04 06:31 UTCEPSS rescore
  18. 2026-07-04 06:31 UTCEPSS rescore
  19. 2026-07-04 02:23 UTCEG score recompute
  20. 2026-07-04 02:23 UTCGHSA enrichment
  21. 2026-07-03 13:16 UTCEG score recompute
  22. 2026-07-03 13:16 UTCGHSA enrichment
  23. 2026-07-03 00:10 UTCEG score recompute
  24. 2026-07-03 00:10 UTCGHSA enrichment
  25. 2026-07-02 11:05 UTCEG score recompute
Show 32 more
  1. 2026-07-02 11:05 UTCGHSA enrichment
  2. 2026-07-01 21:59 UTCEG score recompute
  3. 2026-07-01 21:58 UTCGHSA enrichment
  4. 2026-07-01 15:07 UTCEPSS rescore
  5. 2026-07-01 08:49 UTCEG score recompute
  6. 2026-07-01 08:49 UTCGHSA enrichment
  7. 2026-06-30 23:22 UTCEPSS rescore
  8. 2026-06-30 19:44 UTCEG score recompute
  9. 2026-06-30 19:44 UTCGHSA enrichment
  10. 2026-06-30 06:39 UTCEG score recompute
  11. 2026-06-30 06:39 UTCGHSA enrichment
  12. 2026-06-29 17:32 UTCEG score recompute
  13. 2026-06-29 17:32 UTCGHSA enrichment
  14. 2026-06-29 14:06 UTCEPSS rescore
  15. 2026-06-29 04:27 UTCEG score recompute
  16. 2026-06-29 04:26 UTCGHSA enrichment
  17. 2026-06-28 15:20 UTCEG score recompute
  18. 2026-06-28 15:20 UTCGHSA enrichment
  19. 2026-06-28 14:07 UTCEPSS rescore
  20. 2026-06-28 04:56 UTCEPSS rescore
  21. 2026-06-28 04:56 UTCEPSS rescore
  22. 2026-06-28 02:14 UTCEG score recompute
  23. 2026-06-28 02:14 UTCGHSA enrichment
  24. 2026-06-27 13:07 UTCEG score recompute
  25. 2026-06-27 13:07 UTCGHSA enrichment
  26. 2026-06-27 03:08 UTCEPSS rescore
  27. 2026-06-27 00:02 UTCEG score recompute
  28. 2026-06-27 00:02 UTCGHSA enrichment
  29. 2026-06-26 10:57 UTCEG score recompute
  30. 2026-06-26 10:57 UTCGHSA enrichment
  31. 2026-06-25 19:49 UTCEG score recompute
  32. 2026-06-25 19:49 UTCNVD updatefirst tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-56766?
CVE-2026-56766 is a high vulnerability published on June 25, 2026. 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…
When was CVE-2026-56766 disclosed?
CVE-2026-56766 was first published in the National Vulnerability Database on June 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56766 actively exploited?
CVE-2026-56766 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 37.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-56766?
CVE-2026-56766 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2026-56766?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56766, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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