What is the CVSS score of CVE-2025-4820?

CVE-2025-4820 has a CVSS 3.1 base score of 5.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L. EPSS exploitation probability: 0.3%.

Which versions of Quiche are affected by CVE-2025-4820?

Organizations using Impact Cloudflare quiche should be aware of moderate risk from CVE-2025-4820 rated CVSS 5.3. Exploitation could compromise the security of affected deployments.. A patch is available.

How to fix or mitigate CVE-2025-4820?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Quiche CVE-2025-4820

EUVD-2025-18652 MEDIUM

Allocation of Resources Without Limits or Throttling (CWE-770)

2025-06-18 cna@cloudflare.com

Denial Of Service Debian Quiche Cloudflare

5.3

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

5.3 MEDIUM

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Lifecycle Timeline

Patch available

Apr 16, 2026 - 05:29 EUVD

0.24.4

EUVD ID Assigned

Mar 14, 2026 - 22:49 euvd

EUVD-2025-18652

Analysis Generated

Mar 14, 2026 - 22:49 vuln.today

CVE Published

Jun 18, 2025 - 16:15 nvd

MEDIUM 5.3

DescriptionCVE.org

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.

Analysis

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.

Patches

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

Technical ContextAI

A denial of service vulnerability allows an attacker to disrupt the normal functioning of a system, making it unavailable to legitimate users. This vulnerability is classified as Allocation of Resources Without Limits or Throttling (CWE-770).