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CVE-2025-5399: WebSocket endless loop

7.5 CVSS

Description

Due to a mistake in libcurl's WebSocket code, a malicious server can send a
particularly crafted packet which makes libcurl get trapped in an endless
busy-loop.

There is no other way for the application to escape or exit this loop other
than killing the thread/process.

This might be used to DoS libcurl-using application.

Classification

CVE ID: CVE-2025-5399

CVSS Base Severity: HIGH

CVSS Base Score: 7.5

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

Problem Types

CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')

Affected Products

Vendor: curl

Product: curl

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.05% (probability of being exploited)

EPSS Percentile: 15.49% (scored less or equal to compared to others)

EPSS Date: 2025-06-27 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-5399
https://curl.se/docs/CVE-2025-5399.json
https://curl.se/docs/CVE-2025-5399.html
https://hackerone.com/reports/3168039

Timeline