⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 7.5

How to Fix CVE-2026-40607: Cross-Site Scripting in mantisbt

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 7.5 - High
Actively exploited?Not currently listed in CISA KEV
Affected>= 2.1.0, < 2.28.2
Fixed inversion
Type (CWE)CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

What is CVE-2026-40607?

CVE-2026-40607 is a cross-site scripting (XSS) flaw in mantisbt. The product reflects or stores attacker-controlled input without proper escaping, so a crafted payload runs as JavaScript in the browser of any user who views the affected page. Impact ranges from session theft to full account takeover when an administrator is targeted. Vendor description: Mantis Bug Tracker (MantisBT) is an open source issue tracker. In versions 2.11.0 through 2.28.1, a Stored XSS vulnerability is caused by incorrect escaping of a saved filter's owner, allowing an attacker to inject arbitrary HTML on systems where $g_show_user_realname = ON.

Why this CVE matters

Stored XSS in a content-management product or admin console is a direct route to administrator takeover. Once a payload lands on a page an admin will view, the attacker inherits the same session privileges as the administrator.

For deployments of mantisbt that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open mantisbt's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-40607

  1. Read the vendor advisory in full: https://github.com/mantisbt/mantisbt/security/advisories/GHSA-f633-865q-2mhh
  2. Upgrade mantisbt to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Upgrade mantisbt mantisbt


# CVE-2026-40607 affects mantisbt >= 2.1.0, < 2.28.2.
# Fixed in 2.28.2. Vendor advisory: https://github.com/mantisbt/mantisbt/security/advisories/GHSA-f633-865q-2mhh

# 1. Identify the running version using the vendor-documented command.
#    (Open the product UI -> About, or run the CLI version probe.)

# 2. Stage the patched build named in the advisory.
#    Vendor advisory: https://github.com/mantisbt/mantisbt/security/advisories/GHSA-f633-865q-2mhh

# 3. Apply the upgrade. If the vendor ships a Linux package, pull it via your
#    distribution's package manager:
sudo apt update && sudo apt install --only-upgrade mantisbt        # Debian / Ubuntu
sudo dnf upgrade mantisbt                                          # RHEL / Rocky / Alma / Fedora

# 4. Restart the affected service so the new binary loads.
sudo systemctl restart mantisbt 2>/dev/null || true

# 5. Re-run the version probe and confirm it matches 2.28.2.


# Windows-hosted installs of mantisbt: apply via PSWindowsUpdate or the vendor MSI.
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck -Confirm:$false
Get-WindowsUpdate -AcceptAll -Install -AutoReboot

Verify the fix landed


# CVE-2026-40607 verification checklist.

# 1. Confirm the running version matches 2.28.2 (replace the version probe with
#    the platform-specific command shown above).

# 2. Re-scan the host with your vulnerability scanner (Nessus, Qualys, Tenable,
#    OpenVAS, Wazuh). The scanner must no longer flag CVE-2026-40607.

# 3. Inspect recent service and kernel logs for crash-loops or rollback events.
journalctl -u <service-name> --since "10 minutes ago"
dmesg --since "10 minutes ago"

# 4. Cross-check the running build against the vendor advisory:
#    https://github.com/mantisbt/mantisbt/security/advisories/GHSA-f633-865q-2mhh

If you cannot patch immediately

Disable or restrict access to the affected page or feature for untrusted users until the patch is applied. Add a Content-Security-Policy header that disallows inline scripts and limits script sources to your own domain; this reduces the impact of stored XSS but does not remove the underlying flaw.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for log entries that do not match your normal request patterns, especially repeated requests to the same uncommon endpoint, and any administrative changes you cannot tie back to a known operator.

Frequently asked questions

Is CVE-2026-40607 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-40607?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for mantisbt run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*