CVE-2025-4821
BaseFortify
Publication date: 2025-06-18
Last updated on: 2025-11-06
Assigner: Cloudflare, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| cloudflare | quiche | to 0.24.4 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-770 | The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
CVE-2025-4821 is a vulnerability in the Cloudflare quiche Rust library where the congestion window growth is incorrectly handled. An unauthenticated remote attacker can exploit this by completing a handshake and starting a congestion-controlled data transfer to themselves, then sending ACK frames that acknowledge a large range of packet numbers, including packets never sent. This causes the victim's congestion control to increase the congestion window beyond normal limits, allowing more data to be sent than the network path can support. In extreme cases, this can cause an overflow panic due to the congestion window exceeding internal variable limits. [1]
How can this vulnerability impact me? :
This vulnerability can impact you by causing your system to send data at a rate faster than the network path can support, potentially leading to network congestion or instability. In extreme cases, it may cause an overflow panic in the affected software, which could result in crashes or denial of service conditions. Since the attacker is unauthenticated and requires no user interaction, the risk of exploitation is significant. [1]
How can this vulnerability be detected on my network or system? Can you suggest some commands?
Detection of this vulnerability involves monitoring QUIC traffic for abnormal congestion window growth or unusual ACK frames acknowledging large ranges of packet numbers, including those never sent. Network analysis tools that can inspect QUIC protocol behavior might help identify such anomalies. However, no specific detection commands or tools are provided in the available resources. [1]
What immediate steps should I take to mitigate this vulnerability?
The immediate mitigation step is to upgrade the Cloudflare quiche Rust library to version 0.24.4 or later, which contains the fix for this vulnerability. [1]