CVE-2026-7830

HIGHPre-NVD 7.47.4—
EchelonGraph scoreHIGH confidence

Score 7.4 from GitHub Security Advisory (severity: HIGH) published 2026-07-01. a secondary CVSS source baseline 7.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
7.4
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.4Exploit: NoneExposed: 0

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

UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNC_MsLogonIIAuth). In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer (DH_MAX_BITS controls the prime size). A 64-bit DH key can be broken by Pollard's rho algorithm in under one second on current hardware. Additionally, the private exponent is generated by the rng() function, which multiplies three libc rand() values seeded from time(NULL). With approximately 31 bits of internal state and a time-based seed, the private exponent is recoverable in under a minute by a passive observer. A network attacker who can observe the MS-Logon II handshake (via sniffing, recording, or man-in-the-middle) can derive the shared DH key and decrypt the encapsulated username and password, resulting in full credential disclosure. This affects legacy MS-Logon II connections; MS-Logon III (X25519 + AES-256-GCM) is unaffected.

CVSS v3
7.4
EG Score
7.4(high)
EG Risk
33(Track)
EG Risk 33/100SSVC: 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
Severity74% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
12.6%
KEV
Not listed

Published

July 1, 2026

Last Modified

July 9, 2026

Advisory Details (2)

Auto-updated Jul 1, 2026
No patch confirmed yet.
generic

Home - UltraVNC VNC OFFICIAL SITE, Remote Desktop Free Opensource

https://uvnc.com/
generic

GitHub - ultravnc/UltraVNC: 👁️ UltraVNC Server, UltraVNC Viewer, UltraVNC Repeater and UltraVNC SC | Official repository: https://github.com/ultravnc/UltraVNC · GitHub

https://github.com/ultravnc/UltraVNC

Vendor Advisories for CVE-2026-7830(1)

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

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 66× 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. 2026-07-23 03:23 UTCEG score recompute
  2. 2026-07-22 14:08 UTCEPSS rescore
  3. 2026-07-22 14:08 UTCEPSS rescore
  4. 2026-07-21 15:25 UTCEPSS rescore
  5. 2026-07-21 15:25 UTCEPSS rescore
  6. 2026-07-20 17:08 UTCEPSS rescore
  7. 2026-07-19 14:31 UTCEPSS rescore
  8. 2026-07-19 02:29 UTCEPSS rescore
  9. 2026-07-18 10:04 UTCEPSS rescore
  10. 2026-07-16 19:56 UTCGHSA enrichment
  11. 2026-07-16 17:03 UTCEPSS rescore
  12. 2026-07-16 08:36 UTCGHSA enrichment
  13. 2026-07-15 21:16 UTCGHSA enrichment
  14. 2026-07-15 16:57 UTCEPSS rescore
  15. 2026-07-15 09:56 UTCGHSA enrichment
  16. 2026-07-15 02:00 UTCEPSS rescore
  17. 2026-07-14 22:34 UTCGHSA enrichment
  18. 2026-07-14 11:14 UTCGHSA enrichment
  19. 2026-07-13 23:52 UTCGHSA enrichment
  20. 2026-07-13 22:31 UTCEPSS rescore
  21. 2026-07-13 12:32 UTCGHSA enrichment
  22. 2026-07-13 06:13 UTCEPSS rescore
  23. 2026-07-13 01:12 UTCGHSA enrichment
  24. 2026-07-12 13:52 UTCGHSA enrichment
  25. 2026-07-12 05:46 UTCEPSS rescore
Show 41 more
  1. 2026-07-12 02:27 UTCGHSA enrichment
  2. 2026-07-11 15:07 UTCGHSA enrichment
  3. 2026-07-11 08:27 UTCEPSS rescore
  4. 2026-07-11 03:46 UTCGHSA enrichment
  5. 2026-07-10 16:26 UTCGHSA enrichment
  6. 2026-07-10 05:05 UTCGHSA enrichment
  7. 2026-07-09 19:10 UTCEPSS rescore
  8. 2026-07-09 19:10 UTCEPSS rescore
  9. 2026-07-09 17:46 UTCGHSA enrichment
  10. 2026-07-09 06:22 UTCGHSA enrichment
  11. 2026-07-08 19:01 UTCGHSA enrichment
  12. 2026-07-08 15:16 UTCEPSS rescore
  13. 2026-07-08 15:16 UTCEPSS rescore
  14. 2026-07-08 07:40 UTCGHSA enrichment
  15. 2026-07-07 20:20 UTCGHSA enrichment
  16. 2026-07-07 13:46 UTCEPSS rescore
  17. 2026-07-07 13:46 UTCEPSS rescore
  18. 2026-07-07 08:59 UTCGHSA enrichment
  19. 2026-07-06 21:28 UTCGHSA enrichment
  20. 2026-07-06 16:27 UTCEPSS rescore
  21. 2026-07-06 16:27 UTCEPSS rescore
  22. 2026-07-06 10:07 UTCGHSA enrichment
  23. 2026-07-06 02:23 UTCEPSS rescore
  24. 2026-07-06 02:23 UTCEPSS rescore
  25. 2026-07-05 22:46 UTCGHSA enrichment
  26. 2026-07-05 11:26 UTCGHSA enrichment
  27. 2026-07-05 02:31 UTCEPSS rescore
  28. 2026-07-05 02:30 UTCEPSS rescore
  29. 2026-07-05 00:05 UTCGHSA enrichment
  30. 2026-07-04 12:44 UTCGHSA enrichment
  31. 2026-07-04 06:31 UTCEPSS rescore
  32. 2026-07-04 06:31 UTCEPSS rescore
  33. 2026-07-04 01:24 UTCGHSA enrichment
  34. 2026-07-03 14:04 UTCGHSA enrichment
  35. 2026-07-03 02:45 UTCGHSA enrichment
  36. 2026-07-02 15:23 UTCGHSA enrichment
  37. 2026-07-02 04:02 UTCGHSA enrichment
  38. 2026-07-01 16:41 UTCGHSA enrichment
  39. 2026-07-01 15:07 UTCEPSS rescore
  40. 2026-07-01 05:21 UTCEG score recompute
  41. 2026-07-01 05:20 UTCNVD updatefirst tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-7830?
CVE-2026-7830 is a high vulnerability published on July 1, 2026. UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNCMsLogonIIAuth). In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer (DHMAX_BITS controls the prime size). A 64-bit DH key can be…
When was CVE-2026-7830 disclosed?
CVE-2026-7830 was first published in the National Vulnerability Database on July 1, 2026, with the most recent update on July 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-7830 actively exploited?
CVE-2026-7830 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 12.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-7830?
CVE-2026-7830 has a CVSS v3 base score of 7.4 (NVD).
How do I remediate CVE-2026-7830?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-7830, 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

Explore the affected products and dependency analysis for CVE-2026-7830

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