How severe is CVE-2026-34579?

No CVSS score has been assigned to CVE-2026-34579 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34579?

CVE-2026-34579 affects the following packages: mantisbt/mantisbt (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-34579?

Update mantisbt/mantisbt to 2.28.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34579 is resolved across your whole dependency graph.

How do I detect CVE-2026-34579 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mantisbt/mantisbt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34579 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-34579 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34579 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-34579?

CVE-2026-34579 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 30th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-34579?

CVE-2026-34579 is classified as Information Exposure (CWE-200), CWE-863 (CWE-863). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34579 published, and has it been updated?

CVE-2026-34579 was published on May 19, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-34579: mantisbt — Fixed in 2.28.2

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34579.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐘mantisbt/mantisbt

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.28.1 and prior are vulnerable to Authorization Bypass through the private issue monitoring feature . Using a crafted POST request to bug_monitor_add.php, a user with project-level access can add themselves as a monitor for a private issue they do not have access to. Despite displaying an Access Denied error, the application accepts the request and creates a monitor relationship for the private issue. Direct access to the private issue remains blocked, but the user will receive email notifications for updates, leading to disclosure of the private issue's metadata and content. This issue has been fixed in version 2.28.2.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`mantisbt/mantisbt`	≥ 2.26.1&&< 2.28.2	2.28.2`composer require mantisbt/mantisbt:^2.28.2`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mantisbt/mantisbt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mantisbt/mantisbt to 2.28.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34579 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.28.1 and prior are vulnerable to Authorization Bypass through the private issue monitoring feature . Using a crafted POST request to bug_monitor_add.php, a user with project-level access can add themselves as a monitor for a private issue they do not have access to. Despite displaying an Access Denied error, the application accepts the request and creates a monitor relationship for the private issue. Direct access to the private issue remains blocked, but the user will receive email notifications for updates, leading to

O3 Security · Impact-Aware SCA

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CVE-2026-34579 — mantisbt