MantisBT up to 2.28.3 SOAP API mci_check_login improper authentication

Summaryinfo

A vulnerability, which was classified as critical, was found in MantisBT up to 2.28.3. This affects the function mci_check_login of the component SOAP API. Such manipulation leads to improper authentication. This vulnerability is documented as CVE-2026-47156. The attack can be executed remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in MantisBT up to 2.28.3. Affected by this issue is the function mci_check_login of the component SOAP API. The manipulation with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. CVE summarizes:

MantisBT is an open source bug tracker. Versions 2.28.3 and earlier contain 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. Version 2.28.4 contains a patch. No known workarounds are available.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-47156 since 05/18/2026. The exploitation is known to be easy. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 2.28.4 eliminates this vulnerability.

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Productinfo

Type

• Bug Tracking Software

Name

• MantisBT

Version

• 2.28.0
• 2.28.1
• 2.28.2
• 2.28.3

License

• open-source

Website

• Product: https://github.com/mantisbt/mantisbt/

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