Summary
MantisBT: SOAP API Authentication Bypass with Privilege Escalation to Administrator
MantisBT 2.28.3 and earlier contains a critical authentication bypass in the SOAP API's mci_check_login() function. Any user knowing any valid cookie_string can authenticate as any other user (knowing their username), including the administrator, without knowing the target's password.
The vulnerability is exploitable with zero prior access on default MantisBT installations because self-registration is enabled by default ($g_allow_signup = ON). A self-registered user can use their own cookie_string (readable from their browser's MANTIS_STRING_COOKIE cookie after login) to impersonate the administrator via the SOAP API.
The REST API is NOT affected. The REST API's AuthMiddleware derives the username server-side from the API token or session cookie, so the username cannot be spoofed.
The Web UI is NOT affected. The Web UI authenticates via PHP session cookies (PHPSESSID) and validates the MANTIS_STRING_COOKIE against the logged-in user through auth_is_cookie_valid(). The username is derived server-side from the cookie, not supplied by the client.
Workarounds
None
Resources
Credits
MantisBT would like to thank McCaulay Hudson (@_McCaulay) of watchTowr for originally identifying and responsibly reporting the issue.
The vulnerability was subsequently discovered by other researchers, while the team was working on fixing and preparing the release. MantisBT credits them here, in chronological order of their reports:
- Keitaro Yamazaki (@tyage)
- Harrison Keating (@voraci0us)
- Chandler Johnson (@chndlrx)
- Bharat Devasani (@bharatdevasani)
Impact
- Full administrator access to the SOAP API from zero prior access (with self-registration enabled, which is the default)
- Read/write all issues including private issues and notes across all projects
- Full data exfiltration of all bug reports, attachments, user accounts (id, name, email), and non-private configuration values via the 71 SOAP operations available
- Destructive operations: delete projects, issues, attachments, tags, categories, and versions
- Data manipulation: create/modify issues, impersonate reporters, manage project structure
- Chains with other vulnerabilities: the SOAP admin access enables exploitation of SOAP vulnerabilities that require administrator privileges
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-47156? CVE-2026-47156 is a critical-severity improper authentication vulnerability in mantisbt/mantisbt (composer), affecting versions <= 2.28.3. It is fixed in 2.28.4. The application does not adequately verify the identity of a user, device, or process before granting access.
- Which versions of mantisbt/mantisbt are affected by CVE-2026-47156? mantisbt/mantisbt (composer) versions <= 2.28.3 is affected.
- Is there a fix for CVE-2026-47156? Yes. CVE-2026-47156 is fixed in 2.28.4. Upgrade to this version or later.
- Is CVE-2026-47156 exploitable, and should I be worried? Whether CVE-2026-47156 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-47156 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-47156? Upgrade
mantisbt/mantisbtto 2.28.4 or later.