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
Elevated
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
83%
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 5× in last 7d / 60× 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.

Showing the most recent 100 of 209 total refreshes for this CVE.

  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-10 09:35 UTCEPSS rescore
  3. 2026-09-08 22:01 UTCEPSS rescore
  4. 2026-09-07 16:01 UTCEPSS rescore
  5. 2026-09-06 13:47 UTCEPSS rescore
  6. 2026-09-04 05:07 UTCEPSS rescore
  7. 2026-09-02 14:12 UTCEPSS rescore
  8. 2026-09-01 13:54 UTCEPSS rescore
  9. 2026-09-01 04:40 UTCEPSS rescore
  10. 2026-08-30 19:31 UTCEG score recompute
  11. 2026-08-30 19:31 UTCGHSA enrichment
  12. 2026-08-30 19:17 UTCEPSS rescore
  13. 2026-08-30 01:22 UTCEPSS rescore
  14. 2026-08-28 21:42 UTCEPSS rescore
  15. 2026-08-27 23:17 UTCEG score recompute
  16. 2026-08-27 23:17 UTCGHSA enrichment
  17. 2026-08-27 14:25 UTCEPSS rescore
  18. 2026-08-26 14:46 UTCEPSS rescore
  19. 2026-08-25 13:49 UTCEPSS rescore
  20. 2026-08-24 21:51 UTCEG score recompute
  21. 2026-08-24 21:51 UTCGHSA enrichment
  22. 2026-08-24 04:30 UTCGHSA enrichment
  23. 2026-08-23 13:56 UTCGHSA enrichment
  24. 2026-08-23 00:51 UTCEG score recompute
  25. 2026-08-23 00:51 UTCGHSA enrichment
Show 75 more
  1. 2026-08-23 00:19 UTCEPSS rescore
  2. 2026-08-22 11:24 UTCEG score recompute
  3. 2026-08-22 11:24 UTCGHSA enrichment
  4. 2026-08-21 23:49 UTCEPSS rescore
  5. 2026-08-21 22:19 UTCGHSA enrichment
  6. 2026-08-21 09:13 UTCEG score recompute
  7. 2026-08-21 09:13 UTCGHSA enrichment
  8. 2026-08-20 22:55 UTCEPSS rescore
  9. 2026-08-20 20:07 UTCGHSA enrichment
  10. 2026-08-20 07:02 UTCEG score recompute
  11. 2026-08-20 07:02 UTCGHSA enrichment
  12. 2026-08-19 17:04 UTCEPSS rescore
  13. 2026-08-19 14:42 UTCGHSA enrichment
  14. 2026-08-19 01:17 UTCEG score recompute
  15. 2026-08-19 01:16 UTCGHSA enrichment
  16. 2026-08-18 13:48 UTCEPSS rescore
  17. 2026-08-17 13:47 UTCEPSS rescore
  18. 2026-08-17 09:07 UTCGHSA enrichment
  19. 2026-08-16 20:02 UTCEG score recompute
  20. 2026-08-16 20:02 UTCGHSA enrichment
  21. 2026-08-16 14:56 UTCEPSS rescore
  22. 2026-08-16 06:13 UTCEG score recompute
  23. 2026-08-16 06:13 UTCGHSA enrichment
  24. 2026-08-16 02:14 UTCEPSS rescore
  25. 2026-08-15 17:08 UTCGHSA enrichment
  26. 2026-08-15 04:03 UTCEG score recompute
  27. 2026-08-15 04:03 UTCGHSA enrichment
  28. 2026-08-15 01:30 UTCEPSS rescore
  29. 2026-08-14 14:58 UTCGHSA enrichment
  30. 2026-08-14 01:52 UTCEG score recompute
  31. 2026-08-14 01:52 UTCGHSA enrichment
  32. 2026-08-13 22:00 UTCEPSS rescore
  33. 2026-08-13 12:47 UTCGHSA enrichment
  34. 2026-08-12 23:42 UTCEG score recompute
  35. 2026-08-12 23:42 UTCGHSA enrichment
  36. 2026-08-12 13:51 UTCEPSS rescore
  37. 2026-08-12 10:37 UTCGHSA enrichment
  38. 2026-08-11 21:31 UTCEG score recompute
  39. 2026-08-11 21:31 UTCGHSA enrichment
  40. 2026-08-11 08:26 UTCEG score recompute
  41. 2026-08-11 08:26 UTCGHSA enrichment
  42. 2026-08-11 00:00 UTCEPSS rescore
  43. 2026-08-10 19:21 UTCGHSA enrichment
  44. 2026-08-10 06:15 UTCGHSA enrichment
  45. 2026-08-09 17:10 UTCGHSA enrichment
  46. 2026-08-09 04:05 UTCEG score recompute
  47. 2026-08-09 04:05 UTCGHSA enrichment
  48. 2026-08-08 16:37 UTCEPSS rescore
  49. 2026-08-08 15:00 UTCGHSA enrichment
  50. 2026-08-08 01:54 UTCEG score recompute
  51. 2026-08-08 01:54 UTCGHSA enrichment
  52. 2026-08-07 12:49 UTCGHSA enrichment
  53. 2026-08-06 23:45 UTCEG score recompute
  54. 2026-08-06 23:44 UTCGHSA enrichment
  55. 2026-08-06 13:47 UTCEPSS rescore
  56. 2026-08-06 10:39 UTCGHSA enrichment
  57. 2026-08-05 21:28 UTCEG score recompute
  58. 2026-08-05 21:28 UTCGHSA enrichment
  59. 2026-08-05 19:17 UTCEPSS rescore
  60. 2026-08-05 08:23 UTCEG score recompute
  61. 2026-08-05 08:23 UTCGHSA enrichment
  62. 2026-08-04 15:10 UTCEPSS rescore
  63. 2026-08-04 15:03 UTCEG score recompute
  64. 2026-08-04 15:03 UTCGHSA enrichment
  65. 2026-08-04 10:39 UTCEPSS rescore
  66. 2026-08-03 23:01 UTCEG score recompute
  67. 2026-08-03 23:01 UTCGHSA enrichment
  68. 2026-08-03 10:36 UTCEPSS rescore
  69. 2026-08-03 09:56 UTCGHSA enrichment
  70. 2026-08-02 20:36 UTCGHSA enrichment
  71. 2026-08-02 07:31 UTCEG score recompute
  72. 2026-08-02 07:31 UTCGHSA enrichment
  73. 2026-08-02 02:27 UTCEPSS rescore
  74. 2026-08-01 18:25 UTCGHSA enrichment
  75. 2026-08-01 05:20 UTCEG score recompute

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 16.7% 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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