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CVE-2025-4820

18
FAUCET Score

CVE-2025-4820 affects Cloudflare quiche, where incorrect congestion window growth allows it to send data faster than the network path can support. An unauthenticated remote attacker can exploit this by manipulating the victim's congestion control state through opportunistic ACK attacks, leading to an enlarged congestion window. This vulnerability is rated Medium severity (CVSS 5.3) with a low impact on availability, and there is currently no evidence of active exploitation, public exploit code, or significant community discussion.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.24.4CPE matchmatch criteria
cpe:2.3:a:cloudflare:quiche:*:*:*:*:*:rust:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

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 Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.67%
Probability of exploitation in next 30 days
EPSS Percentile
48.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0067 is in the 30th percentile among its peer group of 23,701 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

github_advisoryvendor investigatingvia nvd_reference
View patch

References

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