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THREATINT
PUBLISHED

CVE-2025-4820

Incorrect congestion window growth by optimistic ACK



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 exercising an opportunistic ACK attack; see RFC 9000 Section 21.4. The victim could grow the congestion window beyond typical expectations and allow more bytes in flight than the path might really support. Patches quiche 0.24.4 is the earliest version containing the fix for this issue.

Reserved 2025-05-16 | Published 2025-06-18 | Updated 2025-06-18 | Assigner cloudflare


MEDIUM: 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Problem types

CWE-770 Allocation of Resources Without Limits or Throttling

Product status

Default status
unaffected

<0.24.4
affected

References

github.com/...quiche/security/advisories/GHSA-2v9p-3p3h-w56j

cve.org (CVE-2025-4820)

nvd.nist.gov (CVE-2025-4820)

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