How severe is CVE-2025-5399?

CVE-2025-5399 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-5399 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-5399?

CVE-2025-5399 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-5399?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-5399 have an EU (EUVD) identifier?

Yes. CVE-2025-5399 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-17371.

When was CVE-2025-5399 published?

CVE-2025-5399 was published on 2025-06-07 and last updated on 2026-06-17.

CVE-2025-5399

CVE-2025-5399 is a high-severity vulnerability in Haxx Curl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-835.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (65th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-17371
Weakness: CWE-835
Affected product: Haxx Curl
Published: 2025-06-07
Last modified: 2026-06-17

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.

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.
How severe is CVE-2025-5399?: CVE-2025-5399 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-5399 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-5399?: CVE-2025-5399 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-5399?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-5399 have an EU (EUVD) identifier?: Yes. CVE-2025-5399 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-17371.
When was CVE-2025-5399 published?: CVE-2025-5399 was published on 2025-06-07 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

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