# CVE-2025-4476: Libsoup: null pointer dereference in libsoup may lead to denial of service

> A malicious server can crash client applications using libsoup by sending a crafted 401 response, causing a denial of service.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 16 May 2025
- **Updated:** 30 Jun 2026
- **Also known as:** AZL-61902, AZL-61910, DEBIAN-CVE-2025-4476, GHSA-qgq4-89p9-qfrh, OESA-2025-2209, OESA-2025-2210, OESA-2025-2279, SUSE-SU-2026:0469-1, UBUNTU-CVE-2025-4476

## What is CVE-2025-4476?

CVE-2025-4476 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 16 May 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A denial-of-service vulnerability has been identified in the libsoup HTTP client library. This flaw can be triggered when a libsoup client receives a 401 (Unauthorized) HTTP response containing a specifically crafted domain parameter within the WWW-Authenticate header. Processing this malformed header can lead to a crash of the client application using libsoup. An attacker could exploit this by setting up a malicious HTTP server. If a user's application using the vulnerable libsoup library connects to this malicious server, it could result in a denial-of-service. Successful exploitation requires tricking a user's client application into connecting to the attacker's malicious server.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-4476?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libsoup` | SUSE:Linux Enterprise Micro 5.2 | All versions | 2.68.4-150200.4.27.1 |

## How do I fix CVE-2025-4476?

Apply the vendor's patch.

## Is CVE-2025-4476 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-4476 exists.

Public exploit code:

- https://github.com/soltanali0/CVE-2025-4476-Exploit (github_poc): https://github.com/soltanali0/CVE-2025-4476-Exploit

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-4476 and fix it if it is affected.

What it is: CVE-2025-4476 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 16 May 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-4476 exists.

Affected product: Red Hat Enterprise Linux 10. 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-2025-4476/ (Markdown: https://insights.sbomify.com/CVE-2025-4476/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-4476
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-4476
- OSV: https://osv.dev/vulnerability/CVE-2025-4476

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-4476/
Summaries are generated and may contain mistakes; the official description above is the record.