CVE-2025-5399

Public Exploit
WebSocket endless loop

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.

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
EPSS 0.02%
Vendor Advisory curl.se Vendor Advisory curl.se
Affected: curl curl
Published at:
Updated at:

References

Link Tags
https://curl.se/docs/CVE-2025-5399.json vendor advisory
https://curl.se/docs/CVE-2025-5399.html vendor advisory
https://hackerone.com/reports/3168039 third party advisory issue tracking exploit
http://www.openwall.com/lists/oss-security/2025/06/04/2 mailing list third party advisory

Frequently Asked Questions

What is the severity of CVE-2025-5399?
CVE-2025-5399 has been scored as a high severity vulnerability.
How to fix CVE-2025-5399?
To fix CVE-2025-5399, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2025-5399 being actively exploited in the wild?
It is possible that CVE-2025-5399 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-5399?
CVE-2025-5399 affects curl curl.
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