# CVE-2026-28368: Undertow: undertow: request smuggling via inconsistent header parsing

> Remote attackers can exploit inconsistent header parsing in Undertow to perform request smuggling, bypassing security controls and accessing unauthorized resources.

- **Severity:** High 8.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Mar 2026
- **Updated:** 14 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-28368, GHSA-8v4x-mgvp-p658, UBUNTU-CVE-2026-28368

## What is CVE-2026-28368?

CVE-2026-28368 is a high-severity vulnerability in Redhat Enterprise Linux, published on 27 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 Undertow. This vulnerability allows a remote attacker to construct specially crafted requests where header names are parsed differently by Undertow compared to upstream proxies. This discrepancy in header interpretation can be exploited to launch request smuggling attacks, potentially bypassing security controls and accessing unauthorized resources.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2026-28368?

2 open source packages ship an affected version, including io.undertow:undertow-parent. It affects 10 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.undertow:undertow-parent` | Maven | All versions to 2.3.23.Final | None |
| `io.undertow:undertow-parent` | Maven | All versions to 2.3.23.Final | None |

Products: Redhat Build of Apache Camel - Hawtio, Redhat Build of Apache Camel for Spring Boot, Redhat Data Grid, Redhat Enterprise Linux, Redhat Fuse, Redhat Jboss Enterprise Application Platform, Redhat Jboss Enterprise Application Platform Expansion Pack, Redhat Process Automation, Redhat Single Sign-On, Redhat Undertow.

## How do I fix CVE-2026-28368?

Apply the vendor's patch.

## Is CVE-2026-28368 being exploited?

There is no known exploitation of CVE-2026-28368 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2026-28367](https://insights.sbomify.com/CVE-2026-28367/): Undertow: undertow: request smuggling via `\r\r\r` as a header block terminator (high 8.7)
- [CVE-2026-28369](https://insights.sbomify.com/CVE-2026-28369/): Undertow: undertow: request smuggling via malformed http request headers (high 8.7)
- [CVE-2024-7885](https://insights.sbomify.com/CVE-2024-7885/): Undertow: improper state management in proxy protocol parsing causes information leakage (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28368 and fix it if it is affected.

What it is: CVE-2026-28368 is a high-severity vulnerability in Redhat Enterprise Linux, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-28368 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.undertow:undertow-parent (Maven): affected all versions up to 2.3.23.Final; no fix listed
- io.undertow:undertow-parent (Maven): affected all versions up to 2.3.23.Final; no fix listed

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-2026-28368/ (Markdown: https://insights.sbomify.com/CVE-2026-28368/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28368
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28368
- OSV: https://osv.dev/vulnerability/CVE-2026-28368

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28368/
Summaries are generated and may contain mistakes; the official description above is the record.