CVE-2025-4821

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.7%, top 50% 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
Trending — 3 sources updated this week
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

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

Impact

Cloudflare quiche was discovered to be vulnerable to incorrect congestion window growth, which could cause it to send data at a rate faster than the path might actually support.

An unauthenticated remote attacker can exploit the vulnerability by first completing a handshake and initiating a congestion-controlled data transfer towards itself. Then, it could manipulate the victim's congestion control state by sending ACK frames covering a large range of packet numbers (including packet numbers that had never been sent); see RFC 9000 Section 19.3. The victim could grow the congestion window beyond typical expectations and allow more bytes in flight than the path might really support. In extreme cases, the window might grow beyond the limit of the internal variable's type, leading to an overflow panic.

Patches

quiche 0.24.4 is the earliest version containing the fix for this issue.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
50.2%
KEV
Not listed

Published

June 18, 2025

Last Modified

November 6, 2025

References (1)

Weakness Classification(1)

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

Data Freshness Timeline

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

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Frequently asked(5)

What is CVE-2025-4821?
CVE-2025-4821 is a high vulnerability published on June 18, 2025. Impact Cloudflare quiche was discovered to be vulnerable to incorrect congestion window growth, which could cause it to send data at a rate faster than the path might actually support. An unauthenticated remote attacker can exploit the vulnerability by first completing a handshake and initiating a…
When was CVE-2025-4821 disclosed?
CVE-2025-4821 was first published in the National Vulnerability Database on June 18, 2025, with the most recent update on November 6, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-4821 actively exploited?
CVE-2025-4821 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 50.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-4821?
CVE-2025-4821 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2025-4821?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-4821, 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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