CVE-2026-40597

CVE-2026-40597 is a high-severity vulnerability with a CVSS 4.0 base score of 7.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

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.

Frequently asked questions

What is CVE-2026-40597?
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.
How severe is CVE-2026-40597?
CVE-2026-40597 has a CVSS 4.0 base score of 7.6, rated high severity.
Is CVE-2026-40597 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-40597?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-40597 have an EU (EUVD) identifier?
Yes. CVE-2026-40597 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31496.
When was CVE-2026-40597 published?
CVE-2026-40597 was published on 2026-05-22 and last updated on 2026-06-17.

References

Other CWE-79 (Cross-site Scripting (XSS)) vulnerabilities

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