CVE-2025-1866

CRITICALNVD 10.010.0—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 10.0 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 68% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
10.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 10.0Exploit: None knownExposed: 0

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

Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability in warmcat libwebsockets allows Pointer Manipulation, potentially leading to out-of-bounds memory access. This issue affects libwebsockets before 4.3.4 and is present in code built specifically for the Win32 platform.

By default, the affected code is not executed unless one of the following conditions is met:

LWS_WITHOUT_EXTENSIONS (default ON) is manually set to OFF in CMake. LWS_WITH_HTTP_STREAM_COMPRESSION (default OFF) is manually set to ON in CMake. Despite these conditions, when triggered in affected configurations, this vulnerability may allow attackers to manipulate pointers, potentially leading to memory corruption or unexpected behavior.

CVSS v3
10.0
EG Score
10.0(medium)
EG Risk
60(Track)
EG Risk 60/100SSVC: 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
Severity100% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
34%
KEV
Not listed

Published

March 3, 2025

Last Modified

April 15, 2026

Advisory Details (1)

Auto-updated Aug 8, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
github_commit

commit 3f7c79fd5733 (warmcat/libwebsockets)

Fix landed in warmcat/libwebsockets commit 3f7c79fd5733 — awaiting tagged release

https://github.com/warmcat/libwebsockets/commit/3f7c79fd57338aca1bf4a1b1f24e324b80d36265

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 41× 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 140 total refreshes for this CVE.

  1. 2026-08-07 16:26 UTCEPSS rescore
  2. 2026-08-06 13:45 UTCEPSS rescore
  3. 2026-08-05 19:16 UTCEPSS rescore
  4. 2026-08-04 15:09 UTCEPSS rescore
  5. 2026-08-04 10:37 UTCEPSS rescore
  6. 2026-08-03 10:35 UTCEPSS rescore
  7. 2026-08-02 02:25 UTCEPSS rescore
  8. 2026-08-01 04:14 UTCEPSS rescore
  9. 2026-08-01 01:12 UTCOSV refresh
  10. 2026-07-30 16:26 UTCEPSS rescore
  11. 2026-07-30 01:29 UTCEPSS rescore
  12. 2026-07-28 15:35 UTCEPSS rescore
  13. 2026-07-27 14:12 UTCEPSS rescore
  14. 2026-07-26 14:53 UTCEPSS rescore
  15. 2026-07-25 14:17 UTCEPSS rescore
  16. 2026-07-24 14:16 UTCEPSS rescore
  17. 2026-07-23 14:17 UTCEPSS rescore
  18. 2026-07-23 02:49 UTCEG score recompute
  19. 2026-07-22 14:07 UTCEPSS rescore
  20. 2026-07-22 14:07 UTCEPSS rescore
  21. 2026-07-21 15:24 UTCEPSS rescore
  22. 2026-07-19 14:30 UTCEPSS rescore
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  24. 2026-07-19 02:28 UTCEPSS rescore
  25. 2026-07-19 02:28 UTCEPSS rescore
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  1. 2026-07-18 10:03 UTCEPSS rescore
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  4. 2026-07-15 16:57 UTCEPSS rescore
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  6. 2026-07-15 01:59 UTCEPSS rescore
  7. 2026-07-15 01:59 UTCEPSS rescore
  8. 2026-07-14 08:40 UTCOSV refresh
  9. 2026-07-13 22:29 UTCEPSS rescore
  10. 2026-07-13 22:29 UTCEPSS rescore
  11. 2026-07-13 06:12 UTCEPSS rescore
  12. 2026-07-12 05:46 UTCEPSS rescore
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  14. 2026-07-11 08:26 UTCEPSS rescore
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  16. 2026-07-09 19:09 UTCEPSS rescore
  17. 2026-07-08 15:14 UTCEPSS rescore
  18. 2026-07-07 13:45 UTCEPSS rescore
  19. 2026-07-06 16:26 UTCEPSS rescore
  20. 2026-07-06 02:22 UTCEPSS rescore
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  22. 2026-07-05 02:30 UTCEPSS rescore
  23. 2026-07-04 06:30 UTCEPSS rescore
  24. 2026-07-01 15:06 UTCEPSS rescore
  25. 2026-06-30 23:21 UTCEPSS rescore
  26. 2026-06-29 14:06 UTCEPSS rescore
  27. 2026-06-28 14:07 UTCEPSS rescore
  28. 2026-06-28 14:07 UTCEPSS rescore
  29. 2026-06-28 04:55 UTCEPSS rescore
  30. 2026-06-27 03:08 UTCEPSS rescore
  31. 2026-06-27 03:08 UTCEPSS rescore
  32. 2026-06-26 09:23 UTCOSV refresh
  33. 2026-06-25 13:49 UTCEPSS rescore
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  35. 2026-06-24 14:04 UTCEPSS rescore
  36. 2026-06-24 14:04 UTCEPSS rescore
  37. 2026-06-23 21:32 UTCEPSS rescore
  38. 2026-06-22 14:25 UTCEPSS rescore
  39. 2026-06-22 14:25 UTCEPSS rescore
  40. 2026-06-21 14:56 UTCEPSS rescore
  41. 2026-06-21 14:56 UTCEPSS rescore
  42. 2026-06-21 01:59 UTCEPSS rescore
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  44. 2026-06-19 19:25 UTCEPSS rescore
  45. 2026-06-19 19:25 UTCEPSS rescore
  46. 2026-06-18 17:52 UTCEPSS rescore
  47. 2026-06-18 17:52 UTCEPSS rescore
  48. 2026-06-17 17:52 UTCEPSS rescore
  49. 2026-06-16 17:52 UTCEPSS rescore
  50. 2026-06-15 17:48 UTCEPSS rescore
  51. 2026-06-14 23:17 UTCEPSS rescore
  52. 2026-06-13 22:59 UTCEPSS rescore
  53. 2026-06-13 22:59 UTCEPSS rescore
  54. 2026-06-12 23:11 UTCEPSS rescore
  55. 2026-06-11 13:59 UTCEPSS rescore
  56. 2026-06-10 22:18 UTCEPSS rescore
  57. 2026-06-10 13:21 UTCEPSS rescore
  58. 2026-06-08 16:28 UTCEG score recompute▲ 10.00
  59. 2026-06-08 16:28 UTCGHSA enrichment
  60. 2026-06-08 14:16 UTCEPSS rescore
  61. 2026-06-08 14:16 UTCEPSS rescore
  62. 2026-06-07 15:24 UTCEPSS rescore
  63. 2026-06-06 13:47 UTCEPSS rescore
  64. 2026-06-06 13:47 UTCEPSS rescore
  65. 2026-06-05 22:46 UTCEPSS rescore
  66. 2026-06-05 22:46 UTCEPSS rescore
  67. 2026-06-05 06:10 UTCEPSS rescore
  68. 2026-06-05 06:10 UTCEPSS rescore
  69. 2026-06-04 13:11 UTCEPSS rescore
  70. 2026-06-04 13:11 UTCEPSS rescore
  71. 2026-06-03 17:39 UTCOSV refresh
  72. 2026-06-02 20:12 UTCEPSS rescore
  73. 2026-06-02 20:12 UTCEPSS rescore
  74. 2026-06-01 13:51 UTCEPSS rescore
  75. 2026-06-01 13:51 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2025-1866?
CVE-2025-1866 is a critical vulnerability published on March 3, 2025. Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability in warmcat libwebsockets allows Pointer Manipulation, potentially leading to out-of-bounds memory access. This issue affects libwebsockets before 4.3.4 and is present in code built specifically for the Win32…
When was CVE-2025-1866 disclosed?
CVE-2025-1866 was first published in the National Vulnerability Database on March 3, 2025, with the most recent update on April 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-1866 actively exploited?
CVE-2025-1866 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 65.8% of all scored CVEs.
What is the CVSS score of CVE-2025-1866?
CVE-2025-1866 has a CVSS v3 base score of 10.0 (NVD).
How do I remediate CVE-2025-1866?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-1866, 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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