How severe is CVE-2026-42071?

No CVSS score has been assigned to CVE-2026-42071 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42071?

CVE-2026-42071 affects the following packages: mantisbt/mantisbt (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-42071?

Update mantisbt/mantisbt to 2.28.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42071 is resolved across your whole dependency graph.

How do I detect CVE-2026-42071 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-2026-42071 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-2026-42071 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42071 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-2026-42071?

CVE-2026-42071 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 18th 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-2026-42071?

CVE-2026-42071 is classified as CWE-862 (CWE-862). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42071 published, and has it been updated?

CVE-2026-42071 was published on May 28, 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.

🐘 Packagist

Not in CISA KEV

CVE-2026-42071 — mantisbt

Fix: mantisbt/mantisbt@029d9d2

CVE-2026-42071 is a CWE-862 vulnerability in mantisbt/mantisbt. A fix is available for mantisbt/mantisbt — see the affected versions and patch details below.

MantisBT: Private Bugnote Attachment Content Leak via REST API

Also known asGHSA-pw5x-2mf9-3xc8

Published

May 28, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
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-2026-42071.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs18th percentile — riskier than 18% 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

Impact

REPORTER (access level 25) can view file attachments that were uploaded to private bugnotes by DEVELOPER/MANAGER/ADMIN users
Private bugnotes are intended for internal developer discussion; their attachments (logs, screenshots, patches) should be equally protected
The web UI is NOT affected — it filters through bugnote_get_all_visible_bugnotes() first

Patches

029d9d203d9e4ae96b3e59d552fa7395cc1e5071

Workarounds

None

Credits

Thanks to the following security researchers for independently discovering and responsibly reporting the issue.

Vishal Shukla
Tristan Madani (@TristanInSec) from Talence Security
Tang Cheuk Hei (@siunam321)

This advisory's contents was largely copied from Tristan's well-written report.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`mantisbt/mantisbt`	≥ 2.23.0&&< 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-2026-42071 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

A missing authorization check in MantisBT's file visibility function allows any authenticated user (REPORTER+) to download attachments on private bugnotes they should not be able to access, via the REST API endpoint GET /api/rest/issues/{id}/files and SOAP API mc_issue_attachment_get endpoint. ### Impact - REPORTER (access level 25) can view file attachments that were uploaded to private bugnotes by DEVELOPER/MANAGER/ADMIN users - Private bugnotes are intended for internal developer discussion; their attachments (logs, screenshots, patches) should be equally protected - The web UI is NOT affe

O3 Security · Impact-Aware SCA

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