Vulnerability

CVE-2025-5399

Low· 7.5CVSS7.5EPSS1%

.rules3/5

curl/libcurl: WebSocket endless loop

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.

Threat signal

75/100

High

Severity

low

CVSS

7.5

EPSS

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

7.5/ 10HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactNoneNo confidentiality impact.
Integrity ImpactNoneNo integrity impact.
Availability ImpactHighTotal loss of availability — full DoS possible.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

0.57%

probability of exploitation in next 30 days

p69

higher than 69% of all CVEs

3-day trend↑ 0pp

Low exploitation likelihood — defer if no other signals fire.

Vendor VEX

No VEX statements published for CVE-2025-5399. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCTrack

Total impact on non-trivial mission systems

exploitation: none
automatable: no
impact: total
mission: support

Lifecycle

2025-06-04Published
2026-04-25Last modified2 sources

References

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.