CVE-2025-4821: cloudflare quiche

Vulnerability summary

CVE-2025-4821 is a high (CVSS 7.5) vulnerability in cloudflare quiche. EPSS estimates a 0.94% chance of exploitation in the next 30 days, higher than 60.1% of scored vulnerabilities.

Timeline

1. 18-06-2025
   PublishedVulnerability first disclosed.
2. 18-06-2025
   Last modifiedVulnerability information updated.

Description

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.

• CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.