# CVE-2026-42193: Plunk: SNS webhook forgery

> Unauthenticated attackers can forge SNS webhooks to manipulate email workflows, unsubscribe contacts, and exhaust billing credits in Plunk.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 May 2026
- **Updated:** 11 May 2026
- **Also known as:** GHSA-9792-w86v-gx53

## What is CVE-2026-42193?

CVE-2026-42193 is a critical missing authorization vulnerability in useplunk plunk, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Plunk is an open-source email platform built on top of AWS SES. Prior to version 0.9.0, the /webhooks/sns endpoint accepts Amazon SNS notification payloads from unauthenticated requests without verifying the SNS signature, certificate, or topic ARN, meaning anyone can forge a valid-looking webhook request. This allows an unauthenticated attacker to spoof SNS events to trigger workflow automations, unsubscribe contacts, manipulate email delivery metrics, and potentially exhaust billing credits. This issue has been patched in version 0.9.0.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-42193?


## How do I fix CVE-2026-42193?

No fix has been published for CVE-2026-42193 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42193 being exploited?

There is no known exploitation of CVE-2026-42193 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42193 and fix it if it is affected.

What it is: CVE-2026-42193 is a critical missing authorization vulnerability in useplunk plunk, published on 8 May 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-2026-42193 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-2026-42193/ (Markdown: https://insights.sbomify.com/CVE-2026-42193/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42193
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42193
- OSV: https://osv.dev/vulnerability/CVE-2026-42193

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42193/
Summaries are generated and may contain mistakes; the official description above is the record.