# CVE-2026-34975: Other in plunk

> Authenticated users can inject arbitrary email headers via CRLF characters in Plunk, enabling sender spoofing and silent forwarding.

- **Severity:** High 8.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-2mvm-rg5v-7hfq

## What is CVE-2026-34975?

CVE-2026-34975 is a high-severity vulnerability in useplunk plunk, published on 6 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Plunk is an open-source email platform built on top of AWS SES. Prior to 0.8.0, a CRLF header injection vulnerability was discovered in SESService.ts, where user-supplied values for from.name, subject, custom header keys/values, and attachment filenames were interpolated directly into raw MIME messages without sanitization. An authenticated API user could inject arbitrary email headers (e.g. Bcc, Reply-To) by embedding carriage return/line feed characters in these fields, enabling silent email forwarding, reply redirection, or sender spoofing. The fix adds input validation at the schema level to reject any of these fields containing \r or \n characters, consistent with the existing validation already applied to the contentId field. This vulnerability is fixed in 0.8.0.

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

## Which versions are affected by CVE-2026-34975?

It affects 1 product.


Products: Useplunk Plunk.

## How do I fix CVE-2026-34975?

No fix has been published for CVE-2026-34975 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-34975 being exploited?

There is no known exploitation of CVE-2026-34975 in the wild and no public exploit code.

Public exploit code:

- CRLF email header injection in Plunk raw MIME construction — CVE-2026-34975 / CVSS 8.5 (github_poc): https://github.com/romain-deperne/CVE-2026-34975

## Other vulnerabilities in useplunk plunk

- [CVE-2026-32096](https://insights.sbomify.com/CVE-2026-32096/): Plunk has SSRF via unvalidated AWS SNS SubscriptionConfirmation in POST /webhooks/sns (critical 9.3)
- [CVE-2026-32095](https://insights.sbomify.com/CVE-2026-32095/): Plunk has Stored Cross-Site Scripting (XSS) via SVG File Upload (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34975 and fix it if it is affected.

What it is: CVE-2026-34975 is a high-severity vulnerability in useplunk plunk, published on 6 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-34975 in the wild and no public exploit code.

Affected product: useplunk plunk. 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-2026-34975/ (Markdown: https://insights.sbomify.com/CVE-2026-34975/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34975
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34975
- OSV: https://osv.dev/vulnerability/CVE-2026-34975

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34975/
Summaries are generated and may contain mistakes; the official description above is the record.