# CVE-2026-3634: Libsoup: libsoup: http header injection and response splitting via crlf injection in content-type header

> Attackers can inject CRLF sequences into Content-Type headers, enabling HTTP header injection and response splitting attacks.

- **Severity:** Low 3.9 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 17 Mar 2026
- **Updated:** 19 Mar 2026
- **Also known as:** AZL-80226, DEBIAN-CVE-2026-3634, ECHO-4911-1ada-38af, GHSA-jx6g-363c-pprr, UBUNTU-CVE-2026-3634

## What is CVE-2026-3634?

CVE-2026-3634 is a low-severity vulnerability in Redhat Enterprise Linux, published on 17 Mar 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

A flaw was found in libsoup. An attacker controlling the value used to set the Content-Type header can inject a Carriage Return Line Feed (CRLF) sequence due to improper input sanitization in the `soup_message_headers_set_content_type()` function. This vulnerability allows for the injection of arbitrary header-value pairs, potentially leading to HTTP header injection and response splitting attacks.

Weakness: CWE-93 (Improper Neutralization of CRLF Sequences)

## Which versions are affected by CVE-2026-3634?

It affects 2 products.


Products: Gnome Libsoup, Redhat Enterprise Linux.

## How do I fix CVE-2026-3634?

Apply the vendor's patch.

## Is CVE-2026-3634 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3634 exists.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2026-102556](https://insights.sbomify.com/CVE-2026-102556/): Libsoup: libsoup: heap buffer overflow from websocket pong signal type confusion (high 8.6)
- [CVE-2026-102557](https://insights.sbomify.com/CVE-2026-102557/): Libsoup: libsoup: heap buffer overflow during websocket message reassembly (high 8.6)
- [CVE-2026-102558](https://insights.sbomify.com/CVE-2026-102558/): Libsoup: libsoup: heap buffer overflow during websocket receive-buffer growth (high 8.6)
- [CVE-2026-102559](https://insights.sbomify.com/CVE-2026-102559/): Libsoup: libsoup: heap buffer overflow during websocket client-frame masking (high 8.6)
- [CVE-2026-102560](https://insights.sbomify.com/CVE-2026-102560/): Libsoup: libsoup: heap buffer overflow during outgoing permessage-deflate buffer growth (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3634 and fix it if it is affected.

What it is: CVE-2026-3634 is a low-severity vulnerability in Redhat Enterprise Linux, published on 17 Mar 2026. An attacker needs administrator access to exploit it, 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-2026-3634 exists.

Affected product: Redhat Enterprise Linux. 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-2026-3634/ (Markdown: https://insights.sbomify.com/CVE-2026-3634/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3634
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3634
- OSV: https://osv.dev/vulnerability/CVE-2026-3634

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3634/
Summaries are generated and may contain mistakes; the official description above is the record.