# CVE-2026-40560: Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence

> Starman allows HTTP request smuggling by mishandling conflicting headers, enabling attackers to bypass security controls via reverse proxies.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 28 Apr 2026
- **Updated:** 29 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-40560, GHSA-gwjf-hg8j-jwvr, MGASA-2026-0119, UBUNTU-CVE-2026-40560, openSUSE-SU-2026:10757-1

## What is CVE-2026-40560?

CVE-2026-40560 is a high-severity vulnerability in MIYAGAWA Starman, published on 28 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence.

Starman incorrectly prioritizes "Content-Length" over "Transfer-Encoding: chunked" when both headers are present in an HTTP request. Per RFC 7230 3.3.3, Transfer-Encoding must take precedence.

An attacker could exploit this to smuggle malicious HTTP requests via a front-end reverse proxy.

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

## Which versions are affected by CVE-2026-40560?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `perl-Starman` | openSUSE:Tumbleweed | All versions | 0.4018-1.1 |

Products: Miyagawa Starman.

## How do I fix CVE-2026-40560?

Upgrade to a fixed version.

## Is CVE-2026-40560 being exploited?

There is no known exploitation of CVE-2026-40560 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40560 and fix it if it is affected.

What it is: CVE-2026-40560 is a high-severity vulnerability in MIYAGAWA Starman, published on 28 Apr 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-2026-40560 in the wild and no public exploit code.

Affected product: MIYAGAWA Starman. 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-2026-40560/ (Markdown: https://insights.sbomify.com/CVE-2026-40560/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40560
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40560
- OSV: https://osv.dev/vulnerability/CVE-2026-40560

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40560/
Summaries are generated and may contain mistakes; the official description above is the record.