# CVE-2026-4271: Libsoup: libsoup: denial of service via use-after-free in http/2 server

> Remote attackers can cause denial of service in applications using libsoup's HTTP/2 server by triggering a use-after-free via crafted requests.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 17 Mar 2026
- **Updated:** 19 May 2026
- **Also known as:** DEBIAN-CVE-2026-4271, ECHO-8792-9c43-a7ba, GHSA-xxmc-fm3p-q3x8, ROOT-OS-DEBIAN-13-CVE-2026-4271, SUSE-SU-2026:21879-1, SUSE-SU-2026:21946-1, SUSE-SU-2026:21951-1, SUSE-SU-2026:21998-1, UBUNTU-CVE-2026-4271, openSUSE-SU-2026:10911-1, openSUSE-SU-2026:20845-1

## What is CVE-2026-4271?

CVE-2026-4271 is a medium-severity use after free vulnerability in Redhat Enterprise Linux, published on 17 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in libsoup, a library for handling HTTP requests. This vulnerability, known as a Use-After-Free, occurs in the HTTP/2 server implementation. A remote attacker can exploit this by sending specially crafted HTTP/2 requests that cause authentication failures. This can lead to the application attempting to access memory that has already been freed, potentially causing application instability or crashes, resulting in a Denial of Service (DoS).

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-4271?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libsoup` | SUSE:Linux Enterprise Server 16.0 | All versions | 3.6.6-160000.2.1 |
| `libsoup` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 3.6.6-160000.2.1 |
| `libsoup` | openSUSE:Tumbleweed | All versions | 3.6.6-5.1 |

Products: Gnome Libsoup, Redhat Enterprise Linux.

## How do I fix CVE-2026-4271?

Apply the vendor's patch.

## Is CVE-2026-4271 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4271 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-2026-4271 and fix it if it is affected.

What it is: CVE-2026-4271 is a medium-severity use after free vulnerability in Redhat Enterprise Linux, published on 17 Mar 2026. 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-2026-4271 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-2026-4271/ (Markdown: https://insights.sbomify.com/CVE-2026-4271/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4271
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4271
- OSV: https://osv.dev/vulnerability/CVE-2026-4271

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4271/
Summaries are generated and may contain mistakes; the official description above is the record.