# CVE-2026-116264: MIME::Field::ParamVal versions before 5.521 for Perl allow one invalid Content-Type parameter to hide the parameters after it, including the multipart boundary.


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-116264, GHSA-8mr9-wfcj-h3rm, UBUNTU-CVE-2026-116264

## What is CVE-2026-116264?

CVE-2026-116264 is a vulnerability, published on 28 Oct 2026. 

### Official description

MIME::Field::ParamVal versions before 5.521 for Perl allow one invalid Content-Type parameter to hide the parameters after it, including the multipart boundary.

Parameter parsing stops at the first parameter whose name it cannot read, such as x:y=1 or a name containing an 8-bit byte, and drops every parameter after it. When the boundary is among them, MIME::Parser keeps the multipart body as a single undecoded part without marking the parse as ambiguous.

Mail readers that skip the invalid parameter still find the boundary. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.

Weakness: CWE-436 (Interpretation Conflict)

## Which versions are affected by CVE-2026-116264?


## How do I fix CVE-2026-116264?

No fix has been published for CVE-2026-116264 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-116264 being exploited?

There is no known exploitation of CVE-2026-116264 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-116264 and fix it if it is affected.

What it is: CVE-2026-116264 is a vulnerability, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-116264 in the wild and no public exploit code.

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-2026-116264/ (Markdown: https://insights.sbomify.com/CVE-2026-116264/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-116264
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116264
- OSV: https://osv.dev/vulnerability/CVE-2026-116264

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-116264/
Summaries are generated and may contain mistakes; the official description above is the record.