What is CVE-2025-4821?

CVE-2025-4821 is a high-severity vulnerability in Cloudflare Quiche, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2025-06-18.

How severe is CVE-2025-4821?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Cloudflare Quiche

CVE-2025-4821

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 v…

EPSS: 0.007 (49.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Cloudflare Quiche — versions <0.24.4

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

cna@cloudflare.com (Vendor Advisory)

Frequently asked questions

What is CVE-2025-4821?: CVE-2025-4821 is a high-severity vulnerability in Cloudflare Quiche, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2025-06-18.
How severe is CVE-2025-4821?: High severity. CVSS v3 base score is 7.5 out of 10.