GHSA-42r6-p4px-qvv6 is a high-severity (CVSS 8.3) vulnerability in TGServiceInterface. A fix is available for TGServiceInterface — see the affected versions and patch details below.
tgstation-server cached user logins in legacy server
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-42r6-p4px-qvv6 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
TGServiceInterfaceReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Please note this advisory is for a historical preexisting issue in the legacy server from 2018. It has long since been triaged. It is being moved here for visibility. The text below is copied from the original issue #690
You can login to the server with any username/password combination if someone else is logged in
An explanation of the bug: Back in 3.2.1.0, in order to accommodate running the Control Panel using Mono some hooks were added to the WCF communication layer. Detailed in this commit: https://github.com/tgstation/tgstation-server/commit/2894ea03d708c7f16bab47ba5020c2ad4c3d5554#diff-0ba090ea7073a3a304dfdbdfc512f733
The bug was in this line: https://github.com/tgstation/tgstation-server/commit/2894ea03d708c7f16bab47ba5020c2ad4c3d5554#diff-0ba090ea7073a3a304dfdbdfc512f733R48 authPolicy is passed in by the framework but the documentation for what the parameter is is virtually non-existent: https://docs.microsoft.com/en-us/dotnet/api/system.servicemodel.serviceauthenticationmanager.authenticate?view=netframework-4.7.2#System_ServiceModel_ServiceAuthenticationManager_Authenticate_System_Collections_ObjectModel_ReadOnlyCollection_System_IdentityModel_Policy_IAuthorizationPolicy__System_Uri_System_ServiceModel_Channels_Message__
Turns out it is a cache of what the previously returned policy was, as Floyd thankfully found out for us. The security patch fixes the issue by creating a new empty list as the return value when password authentication fails as opposed to using the authPolicy parameter.
If you're wondering why this line: https://github.com/tgstation/tgstation-server/commit/2894ea03d708c7f16bab47ba5020c2ad4c3d5554#diff-0ba090ea7073a3a304dfdbdfc512f733R42 didn't prevent the issue. It only invalidated the actual Windows login session, but in the eyes of the server the user was still valid since we just passed that closed handle as a return result. Had access to static files been attempted with a bad login, the request would end up erroring due to trying to impersonate using a closed user token handle.
This has been fixed in 1812a9c6793c8516c138a105ccfb2108164f0eff and versions 3.2.5.0+
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | TGServiceInterface | ≥ 3.2.1.0&&< 3.2.5.0 | 3.2.5.0dotnet add package TGServiceInterface --version 3.2.5.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for TGServiceInterface, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update TGServiceInterface to 3.2.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-42r6-p4px-qvv6 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-42r6-p4px-qvv6 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-42r6-p4px-qvv6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-42r6-p4px-qvv6 in your dependencies?
O3 Security finds GHSA-42r6-p4px-qvv6 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.