# CVE-2025-5399: WebSocket endless loop

> A malicious server can trigger an endless busy-loop in libcurl's WebSocket code, causing a denial of service in applications using the library.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Jun 2025
- **Updated:** 9 Jun 2025
- **Also known as:** ALPINE-CVE-2025-5399, BELL-CVE-2025-5399, CLEANSTART-2026-YU63094, CURL-CVE-2025-5399, DEBIAN-CVE-2025-5399, ECHO-0bd5-994d-5bb9, GHSA-8h93-38hx-vv92, JLSEC-2026-434, MINI-ppm5-3j96-36r2, openSUSE-SU-2025:15213-1

## What is CVE-2025-5399?

CVE-2025-5399 is a high-severity denial of service vulnerability in Haxx Curl, published on 7 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2025-5399?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `curl` | openSUSE:Tumbleweed | All versions | 8.14.1-4.1 |

Products: Haxx Curl.

## How do I fix CVE-2025-5399?

Upgrade to a fixed version.

## Is CVE-2025-5399 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-5399 exists.

## Other vulnerabilities in Haxx Curl

- [CVE-2026-19931](https://insights.sbomify.com/CVE-2026-19931/): Negotiate ambient user conn reuse (critical 9.8)
- [CVE-2026-10536](https://insights.sbomify.com/CVE-2026-10536/): HTTP/2 stream-dependency tree UAF (critical 9.8)
- [CVE-2026-11856](https://insights.sbomify.com/CVE-2026-11856/): cross-origin Digest auth state leak (critical 9.8)
- [CVE-2026-8925](https://insights.sbomify.com/CVE-2026-8925/): SASL double-free (critical 9.8)
- [CVE-2026-9079](https://insights.sbomify.com/CVE-2026-9079/): stale proxy password leak (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-5399 and fix it if it is affected.

What it is: CVE-2025-5399 is a high-severity denial of service vulnerability in Haxx Curl, published on 7 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-5399 exists.

Affected product: Haxx Curl. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-5399/ (Markdown: https://insights.sbomify.com/CVE-2025-5399/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-5399
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-5399
- OSV: https://osv.dev/vulnerability/CVE-2025-5399

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-5399/
Summaries are generated and may contain mistakes; the official description above is the record.