CVE-2026-56766

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM 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 weekElevated
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 2%CVSS: 8.8Exploit: Elevated riskExposed: 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(medium)
EG Risk
56(Track)
EG Risk 56/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
2%
EPSS %ILE
78%
KEV
Not listed

Published

June 25, 2026

Last Modified

July 14, 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 16× in last 7d / 85× 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. 2026-07-28 06:25 UTCGHSA enrichment
  2. 2026-07-27 17:17 UTCEG score recompute
  3. 2026-07-27 17:17 UTCGHSA enrichment
  4. 2026-07-27 14:14 UTCEPSS rescore
  5. 2026-07-27 04:04 UTCGHSA enrichment
  6. 2026-07-26 14:56 UTCEG score recompute
  7. 2026-07-26 14:56 UTCGHSA enrichment
  8. 2026-07-26 14:54 UTCEPSS rescore
  9. 2026-07-26 14:54 UTCEPSS rescore
  10. 2026-07-25 14:18 UTCEPSS rescore
  11. 2026-07-25 14:18 UTCEPSS rescore
  12. 2026-07-24 14:18 UTCEPSS rescore
  13. 2026-07-23 14:18 UTCEPSS rescore
  14. 2026-07-23 03:20 UTCEG score recompute
  15. 2026-07-22 14:08 UTCEPSS rescore
  16. 2026-07-21 15:25 UTCEPSS rescore
  17. 2026-07-20 17:08 UTCEPSS rescore
  18. 2026-07-19 14:31 UTCEPSS rescore
  19. 2026-07-19 14:31 UTCEPSS rescore
  20. 2026-07-19 02:29 UTCEPSS rescore
  21. 2026-07-18 10:04 UTCEPSS rescore
  22. 2026-07-17 05:15 UTCGHSA enrichment
  23. 2026-07-16 17:03 UTCEPSS rescore
  24. 2026-07-16 16:10 UTCGHSA enrichment
  25. 2026-07-16 03:02 UTCGHSA enrichment
Show 69 more
  1. 2026-07-15 16:57 UTCEPSS rescore
  2. 2026-07-15 16:57 UTCEPSS rescore
  3. 2026-07-15 13:55 UTCGHSA enrichment
  4. 2026-07-15 02:00 UTCEPSS rescore
  5. 2026-07-15 02:00 UTCEPSS rescore
  6. 2026-07-15 00:49 UTCGHSA enrichment
  7. 2026-07-14 11:33 UTCGHSA enrichment
  8. 2026-07-13 22:31 UTCEPSS rescore
  9. 2026-07-13 22:28 UTCGHSA enrichment
  10. 2026-07-13 09:23 UTCGHSA enrichment
  11. 2026-07-13 06:13 UTCEPSS rescore
  12. 2026-07-13 06:13 UTCEPSS rescore
  13. 2026-07-12 20:17 UTCGHSA enrichment
  14. 2026-07-12 07:11 UTCGHSA enrichment
  15. 2026-07-12 05:46 UTCEPSS rescore
  16. 2026-07-11 18:05 UTCGHSA enrichment
  17. 2026-07-11 08:27 UTCEPSS rescore
  18. 2026-07-11 08:27 UTCEPSS rescore
  19. 2026-07-11 04:59 UTCGHSA enrichment
  20. 2026-07-10 15:54 UTCGHSA enrichment
  21. 2026-07-10 02:48 UTCGHSA enrichment
  22. 2026-07-09 19:10 UTCEPSS rescore
  23. 2026-07-09 19:10 UTCEPSS rescore
  24. 2026-07-09 13:39 UTCGHSA enrichment
  25. 2026-07-09 00:33 UTCGHSA enrichment
  26. 2026-07-08 15:16 UTCEPSS rescore
  27. 2026-07-08 15:16 UTCEPSS rescore
  28. 2026-07-08 11:26 UTCGHSA enrichment
  29. 2026-07-07 22:21 UTCGHSA enrichment
  30. 2026-07-07 13:46 UTCEPSS rescore
  31. 2026-07-07 13:46 UTCEPSS rescore
  32. 2026-07-07 09:15 UTCGHSA enrichment
  33. 2026-07-06 20:09 UTCGHSA enrichment
  34. 2026-07-06 16:27 UTCEPSS rescore
  35. 2026-07-06 16:27 UTCEPSS rescore
  36. 2026-07-06 06:59 UTCGHSA enrichment
  37. 2026-07-06 02:23 UTCEPSS rescore
  38. 2026-07-06 02:23 UTCEPSS rescore
  39. 2026-07-05 17:54 UTCGHSA enrichment
  40. 2026-07-05 04:49 UTCGHSA enrichment
  41. 2026-07-05 02:31 UTCEPSS rescore
  42. 2026-07-05 02:30 UTCEPSS rescore
  43. 2026-07-04 15:29 UTCGHSA enrichment
  44. 2026-07-04 06:31 UTCEPSS rescore
  45. 2026-07-04 06:31 UTCEPSS rescore
  46. 2026-07-04 02:23 UTCGHSA enrichment
  47. 2026-07-03 13:16 UTCGHSA enrichment
  48. 2026-07-03 00:10 UTCGHSA enrichment
  49. 2026-07-02 11:05 UTCGHSA enrichment
  50. 2026-07-01 21:58 UTCGHSA enrichment
  51. 2026-07-01 15:07 UTCEPSS rescore
  52. 2026-07-01 08:49 UTCGHSA enrichment
  53. 2026-06-30 23:22 UTCEPSS rescore
  54. 2026-06-30 19:44 UTCGHSA enrichment
  55. 2026-06-30 06:39 UTCGHSA enrichment
  56. 2026-06-29 17:32 UTCGHSA enrichment
  57. 2026-06-29 14:06 UTCEPSS rescore
  58. 2026-06-29 04:26 UTCGHSA enrichment
  59. 2026-06-28 15:20 UTCGHSA enrichment
  60. 2026-06-28 14:07 UTCEPSS rescore
  61. 2026-06-28 04:56 UTCEPSS rescore
  62. 2026-06-28 04:56 UTCEPSS rescore
  63. 2026-06-28 02:14 UTCGHSA enrichment
  64. 2026-06-27 13:07 UTCGHSA enrichment
  65. 2026-06-27 03:08 UTCEPSS rescore
  66. 2026-06-27 00:02 UTCGHSA enrichment
  67. 2026-06-26 10:57 UTCGHSA enrichment
  68. 2026-06-25 19:49 UTCEG score recompute
  69. 2026-06-25 19:49 UTCNVD updatefirst tracked

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-52622
    First seen Jul 7, 2026

    Hydra - Stack Buffer Overflow

    Open source ↗

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, with the most recent update on July 14, 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 2% probability of exploitation in the next 30 days, which ranks it in the top 21.5% of all scored CVEs.
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.

Dependency Blast Radius

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