MantisBT is Vulnerable to Stored HTML Injection/XSS in Clone Issue Form

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.6 · CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-34463: 0.44% estimated exploitation activity in the next 30 days; percentile 38.68 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

When cloning an issue originating from a Project other than the current one, the clone form (bugreportpage.php) prepends the source Project name before the category selector without proper escaping, allowing an attacker able to to inject HTML if they can set the Project's name (which typically requires manager or administrator access level). Impact Cross-site scripting (XSS). This is mitigated by Content Security Policy which restricts scripts execution. Patches - df22697ae497ddd93f3d9132fdf4979db8d081cd Workarounds Make sure Project names do not contain any HTML tags. Credits Thanks to Vishal Shukla for discovering and responsibly reporting the issue. The vulnerability was also identified and independently reported by @siunam321 (Tang Cheuk Hei), prior to this Advisory's publication.

Published by the source

11 May 2026, 19:32 UTC

Last modified by the source

5 Jun 2026, 14:12 UTC

Source last checked

26 Oct 2026, 14:48 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fvjf-68wh-rwp2

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# Patch Next advisory brief: CVE-2026-34463

Advisory: MantisBT is Vulnerable to Stored HTML Injection/XSS in Clone Issue Form
IDs: CVE-2026-34463, GHSA-fvjf-68wh-rwp2
Record: https://patchnext.com/advisories/cve-2026-34463 (revision 1, source checked 26 Oct 2026, 14:48 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mantisbt/mantisbt 2.28.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist mantisbt/mantisbt: affected <= 2.28.1; fixed in 2.28.2

## Suggested inspection (read-only)
- Packagist mantisbt/mantisbt: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mantisbt/mantisbt.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fvjf-68wh-rwp2 (GitHub-reviewed advisory GHSA-fvjf-68wh-rwp2 lists affected ranges: Packagist mantisbt/mantisbt >=0 <=2.28.1)

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