CVE-2025-5399: WebSocket endless loop
Vulnerability summary
CVE-2025-5399 is a high (CVSS 7.5) Loop with Unreachable Exit Condition vulnerability in curl. EPSS estimates a 1.44% chance of exploitation in the next 30 days, higher than 73.1% of scored vulnerabilities. 1 public exploit is recorded.
Public exploit (reference, Date unknown)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 07-06-2025PublishedVulnerability first disclosed.
- 09-06-2025Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · AlpineEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
1.44%
Chance of exploitation in the next 30 days
Percentile
73%
Versus all other CVEs
30-day change
Increase +0.06 pp
From 1.38% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundExploit Reference (hackerone.com)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Alpine1 product
- curl≥ 8.13.0, < 8.14.1-r0
Curl1 product
- curl8.14.0 | 8.13.0
Debian1 product
- curl< 8.14.1-1
Haxx1 product
- curl≥ 8.13.0, < 8.14.1
Opensuse1 product
- curl&distro=openSUSE Tumbleweed< 8.14.1-4.1
5 vendors · 5 products
References
7 links- curl.se/docs/CVE-2025-5399.jsonVendor Advisory
- curl.se/docs/CVE-2025-5399.htmlVendor Advisory
