---
title: "CVE-2026-47156: MantisBT: SOAP API Authentication Bypass with Privilege Escalation to Administrator"
url: https://erroneo.us/security/cve/CVE-2026-47156/
description: "CVE-2026-47156 (mantisbt/mantisbt (Composer (PHP))): MantisBT is an open source bug tracker. Versions 2.28.3 and earlier contain a critical authentication…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-09
date_modified: 2026-09-10
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-47156"
kev: false
cvss: 9.3
epss: 0.00686
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-47156: MantisBT: SOAP API Authentication Bypass with Privilege Escalation to Administrator

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.7% , percentile 52: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 52% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes mantisbt/mantisbt (Composer (PHP)) <= 2.28.3, fixed in 2.28.4 . Check your lockfile, including transitive dependencies.

## What it is

MantisBT is an open source bug tracker. Versions 2.28.3 and earlier contain a critical authentication bypass in the SOAP API's mcichecklogin() function. Any user knowing any valid cookiestring 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 ($gallowsignup = ON). A self-registered user can use their own cookiestring (readable from their browser's MANTISSTRINGCOOKIE 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 MANTISSTRINGCOOKIE against the logged-in user through authiscookievalid(). 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.

## Affected packages

- Composer (PHP) `mantisbt/mantisbt` <= 2.28.3 → fixed: 2.28.4

## Affected products (CVE record)

- mantisbt mantisbt: < 2.28.4

## Severity

- GitHub_M CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.69% probability of exploitation activity in the next 30 days; percentile 52.

## Sources

- [GitHub Advisory GHSA-c2xg-qjqw-2v98](https://github.com/advisories/GHSA-c2xg-qjqw-2v98)
- [CVE.org record CVE-2026-47156](https://www.cve.org/CVERecord?id=CVE-2026-47156)
- [NVD entry CVE-2026-47156](https://nvd.nist.gov/vuln/detail/CVE-2026-47156)
- [github.com](https://github.com/mantisbt/mantisbt/security/advisories/GHSA-c2xg-qjqw-2v98)
- [github.com](https://github.com/mantisbt/mantisbt/commit/e3571c319b1721b41b0dc4b5b5203cbdcbe0c2ee)
- [mantisbt.org](https://mantisbt.org/bugs/view.php?id=37121)

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Source page: https://erroneo.us/security/cve/CVE-2026-47156/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt