Cloudflare quiche up to 0.24.3 Congestion Window Growth allocation of resources

Summaryinfo

A vulnerability identified as problematic has been detected in Cloudflare quiche up to 0.24.3. The affected element is an unknown function of the component Congestion Window Growth. This manipulation causes allocation of resources. This vulnerability is handled as CVE-2025-4820. The attack can be initiated remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in Cloudflare quiche up to 0.24.3 and classified as problematic. Affected by this vulnerability is some unknown functionality of the component Congestion Window Growth. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2025-4820 since 05/16/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 0.24.4 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-18652). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Cloud Software

Vendor

• Cloudflare

Name

• quiche

Version

• 0.24.0
• 0.24.1
• 0.24.2
• 0.24.3

Website

• Product: https://github.com/cloudflare/quiche/

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Be aware that VulDB is the high quality source for vulnerability data.

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