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

> Attackers can bypass SOAP API authentication to impersonate administrators and escalate privileges in MantisBT installations with default settings.

- **Severity:** Critical 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Sep 2026
- **Updated:** 10 Sep 2026
- **Also known as:** GHSA-c2xg-qjqw-2v98

## What is CVE-2026-47156?

CVE-2026-47156 is a critical authentication bypass vulnerability in mantisbt, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-47156?

2 open source packages ship an affected version, including mantisbt/mantisbt.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mantisbt/mantisbt` | Packagist | All versions | 2.28.4 |
| `mantisbt/mantisbt` | Packagist | All versions | 2.28.4 |

## How do I fix CVE-2026-47156?

Upgrade mantisbt/mantisbt to 2.28.4 or later.

## Is CVE-2026-47156 being exploited?

There is no known exploitation of CVE-2026-47156 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47156 and fix it if it is affected.

What it is: CVE-2026-47156 is a critical authentication bypass vulnerability in mantisbt, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-47156 in the wild and no public exploit code.

Affected packages and fixed versions:
- mantisbt/mantisbt (Packagist): affected all versions; fixed in 2.28.4
- mantisbt/mantisbt (Packagist): affected all versions; fixed in 2.28.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47156/ (Markdown: https://insights.sbomify.com/CVE-2026-47156/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47156
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47156
- OSV: https://osv.dev/vulnerability/CVE-2026-47156

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47156/
Summaries are generated and may contain mistakes; the official description above is the record.