CVE-2026-44040

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 67% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 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 a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes() function seeds libc rand() with time(0) + getpid() + rand() and generates a 16-byte challenge. The combined seed space is approximately 31 bits (libc rand() internal state) and is entirely determined by publicly-observable values (wall-clock time and process ID). An attacker who can observe the authentication exchange can enumerate the seed space and predict the challenge within seconds, enabling forgery or offline brute-forcing of responses. Note: on Windows, the active code path may use vncEncryptBytes2.cpp which calls CryptGenRandom; reachability on shipped Windows binaries requires compile-graph verification and is under investigation.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
33%
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-2026-44040(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 / 84× 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 134 total refreshes for this CVE.

  1. 2026-08-25 13:49 UTCEPSS rescore
  2. 2026-08-25 04:41 UTCEG score recompute
  3. 2026-08-25 04:41 UTCGHSA enrichment
  4. 2026-08-24 05:41 UTCGHSA enrichment
  5. 2026-08-23 06:38 UTCEG score recompute
  6. 2026-08-23 06:38 UTCGHSA enrichment
  7. 2026-08-23 00:19 UTCEPSS rescore
  8. 2026-08-22 07:28 UTCEG score recompute
  9. 2026-08-22 07:28 UTCGHSA enrichment
  10. 2026-08-21 23:49 UTCEPSS rescore
  11. 2026-08-21 04:41 UTCEG score recompute
  12. 2026-08-21 04:41 UTCGHSA enrichment
  13. 2026-08-20 22:55 UTCEPSS rescore
  14. 2026-08-20 04:51 UTCEG score recompute
  15. 2026-08-20 04:51 UTCGHSA enrichment
  16. 2026-08-19 17:04 UTCEPSS rescore
  17. 2026-08-18 22:54 UTCEG score recompute
  18. 2026-08-18 22:54 UTCGHSA enrichment
  19. 2026-08-18 13:48 UTCEPSS rescore
  20. 2026-08-17 23:39 UTCEG score recompute
  21. 2026-08-17 23:39 UTCGHSA enrichment
  22. 2026-08-17 13:47 UTCEPSS rescore
  23. 2026-08-16 20:09 UTCEG score recompute
  24. 2026-08-16 20:09 UTCGHSA enrichment
  25. 2026-08-16 14:56 UTCEPSS rescore
Show 75 more
  1. 2026-08-16 02:14 UTCEPSS rescore
  2. 2026-08-15 21:08 UTCEG score recompute
  3. 2026-08-15 21:08 UTCGHSA enrichment
  4. 2026-08-15 01:30 UTCEPSS rescore
  5. 2026-08-14 22:07 UTCGHSA enrichment
  6. 2026-08-13 22:59 UTCEG score recompute
  7. 2026-08-13 22:59 UTCGHSA enrichment
  8. 2026-08-13 22:00 UTCEPSS rescore
  9. 2026-08-12 23:59 UTCEG score recompute
  10. 2026-08-12 23:59 UTCGHSA enrichment
  11. 2026-08-12 13:51 UTCEPSS rescore
  12. 2026-08-12 00:58 UTCEG score recompute
  13. 2026-08-12 00:58 UTCGHSA enrichment
  14. 2026-08-11 13:43 UTCEPSS rescore
  15. 2026-08-11 01:58 UTCEG score recompute
  16. 2026-08-11 01:58 UTCGHSA enrichment
  17. 2026-08-11 00:00 UTCEPSS rescore
  18. 2026-08-10 02:58 UTCEG score recompute
  19. 2026-08-10 02:58 UTCGHSA enrichment
  20. 2026-08-09 13:46 UTCEPSS rescore
  21. 2026-08-09 03:57 UTCEG score recompute
  22. 2026-08-09 03:57 UTCGHSA enrichment
  23. 2026-08-08 16:37 UTCEPSS rescore
  24. 2026-08-08 04:57 UTCEG score recompute
  25. 2026-08-08 04:57 UTCGHSA enrichment
  26. 2026-08-07 05:56 UTCEG score recompute
  27. 2026-08-07 05:56 UTCGHSA enrichment
  28. 2026-08-06 13:46 UTCEPSS rescore
  29. 2026-08-06 06:56 UTCEG score recompute
  30. 2026-08-06 06:56 UTCGHSA enrichment
  31. 2026-08-05 19:17 UTCEPSS rescore
  32. 2026-08-05 07:56 UTCEG score recompute
  33. 2026-08-05 07:55 UTCGHSA enrichment
  34. 2026-08-04 15:10 UTCEPSS rescore
  35. 2026-08-04 10:38 UTCEPSS rescore
  36. 2026-08-04 08:40 UTCEG score recompute
  37. 2026-08-04 08:40 UTCGHSA enrichment
  38. 2026-08-03 10:36 UTCEPSS rescore
  39. 2026-08-03 08:30 UTCGHSA enrichment
  40. 2026-08-02 09:22 UTCEG score recompute
  41. 2026-08-02 09:22 UTCGHSA enrichment
  42. 2026-08-02 02:27 UTCEPSS rescore
  43. 2026-08-01 10:21 UTCEG score recompute
  44. 2026-08-01 10:21 UTCGHSA enrichment
  45. 2026-08-01 04:16 UTCEPSS rescore
  46. 2026-07-31 11:21 UTCEG score recompute
  47. 2026-07-31 11:21 UTCGHSA enrichment
  48. 2026-07-30 16:28 UTCEPSS rescore
  49. 2026-07-30 12:17 UTCEG score recompute
  50. 2026-07-30 12:17 UTCGHSA enrichment
  51. 2026-07-30 01:30 UTCEPSS rescore
  52. 2026-07-29 13:00 UTCEG score recompute
  53. 2026-07-29 13:00 UTCGHSA enrichment
  54. 2026-07-28 15:36 UTCEPSS rescore
  55. 2026-07-28 13:59 UTCEG score recompute
  56. 2026-07-28 13:59 UTCGHSA enrichment
  57. 2026-07-27 14:13 UTCEPSS rescore
  58. 2026-07-27 12:31 UTCEG score recompute
  59. 2026-07-27 12:31 UTCGHSA enrichment
  60. 2026-07-26 14:54 UTCEPSS rescore
  61. 2026-07-26 14:54 UTCEPSS rescore
  62. 2026-07-26 13:31 UTCEG score recompute
  63. 2026-07-26 13:31 UTCGHSA enrichment
  64. 2026-07-25 14:18 UTCEPSS rescore
  65. 2026-07-24 14:17 UTCEPSS rescore
  66. 2026-07-23 14:18 UTCEPSS rescore
  67. 2026-07-23 03:14 UTCEG score recompute▲ 1.70
  68. 2026-07-22 14:08 UTCEPSS rescore
  69. 2026-07-21 15:24 UTCEPSS rescore
  70. 2026-07-20 17:08 UTCEPSS rescore
  71. 2026-07-19 14:31 UTCEPSS rescore
  72. 2026-07-19 02:29 UTCEPSS rescore
  73. 2026-07-18 10:04 UTCEPSS rescore
  74. 2026-07-16 17:03 UTCEPSS rescore
  75. 2026-07-16 13:41 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2026-44040?
CVE-2026-44040 is a medium vulnerability published on July 1, 2026. UltraVNC through 1.8.2.2 uses a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes() function seeds libc rand() with time(0) + getpid() + rand() and generates a 16-byte challenge. The combined seed space…
When was CVE-2026-44040 disclosed?
CVE-2026-44040 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-2026-44040 actively exploited?
CVE-2026-44040 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 67.4% of all scored CVEs.
What is the CVSS score of CVE-2026-44040?
CVE-2026-44040 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-44040?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-44040, 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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