# Mailpit has an SMTP Header Injection via Regex Bypass in github.com/axllent/mailpit

Advisory record · `GHSA-54wq-72mp-cq7c`

- **Identifiers:** `GHSA-54wq-72mp-cq7c` · `CVE-2026-23829` · `GO-2026-4333`
- **State:** Confirmed
- **Severity:** CVSS 5.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-93](https://cwe.mitre.org/data/definitions/93.html) · [CWE-150](https://cwe.mitre.org/data/definitions/150.html)
- **Tags:** [Other injection](https://agentprime.io/advisories/tag/injection.md) · [CWE-150](https://agentprime.io/advisories/tag/cwe-150.md)
- **Published:** 3 Feb 2026
- **Updated:** 3 Mar 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 3 Feb 2026, 20:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/axllent/mailpit` (Go): affected `<1.28.3`; fixed in `1.28.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 5.3 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.014, the 72nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 3 Feb 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-54wq-72mp-cq7c](https://github.com/advisories/GHSA-54wq-72mp-cq7c)
- [OSV: GHSA-54wq-72mp-cq7c](https://osv.dev/vulnerability/GHSA-54wq-72mp-cq7c)
- <https://github.com/axllent/mailpit/security/advisories/GHSA-54wq-72mp-cq7c>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-23829>
- <https://github.com/axllent/mailpit/commit/36cc06c125954dec6673219dafa084e13cc14534>
- <https://github.com/axllent/mailpit/releases/tag/v1.28.3>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-54wq-72mp-cq7c>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-54wq-72mp-cq7c/>. Everything for agents: <https://agentprime.io/llms.txt>.