CVE-2025-4820
5.3 · MEDIUMOverview
CVE-2025-4820 is a medium-severity vulnerability affecting cloudflare quiche. It was published on June 18, 2025 and has a CVSS 3.1 base score of 5.3 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from cloudflare. Update quiche to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| cloudflare | quiche | >= 0, < 0.24.4 | Affected |
Frequently Asked Questions
What is CVE-2025-4820?
CVE-2025-4820 is a medium-severity vulnerability affecting cloudflare quiche. It was published on June 18, 2025 and has a CVSS 3.1 base score of 5.3 (MEDIUM).
How severe is CVE-2025-4820?
This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2025-4820?
Check the references section for vendor advisories and patches from cloudflare. Update quiche to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-4820?
CyberStrike's AI-powered security agents can automatically detect CVE-2025-4820 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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