CVE-2025-5399 | WebSocket endless loop

Exp

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.

Published: 2025-06-07 Last update: 2025-07-30 Assigner: 2499f714-1537-4658-8207-48ae4bb9eae9 Source: 2499f714-1537-4658-8207-48ae4bb9eae9
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-5399 is rated High Exploit Risk (69.1/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.57%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2025-5399

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2025-5399

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-01 0.49% 0.57% +0.08%
2 2026-04-03 0.19% 0.49% +0.29%
3 2026-03-04 — 0.19% —

Full EPSS history (19 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-5399

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-5399

OS Trackers for CVE-2025-5399

vendor priority summary link
alpine — CVE-2025-5399: 1 source package rows (curl); 263 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 5, open 258. https://security.alpinelinux.org/vuln/CVE-2025-5399
debian unimportant CVE-2025-5399 unimportant priority: Debian including 1 source packages (curl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-5399
redhat medium — https://access.redhat.com/security/cve/CVE-2025-5399
suse medium CVE-2025-5399 severity moderate: SUSE including 305 source package names (0.0.17-1.1:curl-8.14.1-150600.4.28.1, 0.0.17-1.1:libcurl4-8.14.1-150600.4.28.1, …), 579 product×package rows across 149 product lines (Container bci/spack, Container containers/lmcache-lmstack-router, … (149 product lines)): Fixed 254, Known Affected 231, Known Not Affected 94. https://www.suse.com/security/cve/CVE-2025-5399/
ubuntu low CVE-2025-5399 low priority: Ubuntu including 1 source packages (curl), 9 status rows across 9 suites (bionic, focal, jammy, noble, oracular, plucky, trusty, upstream, xenial): not-affected 8, released 1. https://ubuntu.com/security/CVE-2025-5399

Affected software / configurations for CVE-2025-5399

Vendor Product Version Raw CPE
haxx curl >= 8.13.0, < 8.14.1 cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

References for CVE-2025-5399

URL Tags
https://curl.se/docs/CVE-2025-5399.html Vendor Advisory
https://curl.se/docs/CVE-2025-5399.json Vendor Advisory
https://hackerone.com/reports/3168039 Exploit Issue Tracking Third Party Advisory
http://www.openwall.com/lists/oss-security/2025/06/04/2 Mailing List Third Party Advisory
cvelogic Threat Intelligence