CVE-2025-5399
WebSocket endless loop
CVSS v3
7.5
HIGH
EPSS Score
1.4 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
poc
SSVC status
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.
Technical details
- Published
- 2025-06-07
- Last Modified
- 2025-07-30
Frequently asked questions
What is CVE-2025-5399?
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.
Is CVE-2025-5399 actively exploited?
A proof-of-concept exploit exists for CVE-2025-5399, but active exploitation has not been confirmed at this time.
What is the CVSS score for CVE-2025-5399?
CVE-2025-5399 has a CVSS v3 base score of 7.5 (HIGH severity).
Is CVE-2025-5399 affecting your environment?
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