CVE-2025-4820
mediumpriority · track · 0EPSS 0.009 · 58 %ileEUUSEPSS · scored 2026-10-23
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
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affected products (2)
Products and version ranges known to be affected.
also known as (2)
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sources
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references (4)
External citations — patches, advisories, analysis.
- https://github.com/cloudflare/quiche/releasesPatchcnnvd
- https://github.com/cloudflare/quiche/security/advisories/GHSA-2v9p-3p3h-w56jcnnvd
- https://github.com/cloudflare/quiche/security/advisories/GHSA-2v9p-3p3h-w56jenisa_euvd
- https://github.com/cloudflare/quiche/security/advisories/GHSA-2v9p-3p3h-w56jVendor Advisorynvd
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