CVE-2018-17107 is a critical-severity (CVSS 9.8) 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
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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 |
Affected Products
tgstation-servertgstation13Detection & 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 CVE-2018-17107 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.
Frequently Asked Questions
Is CVE-2018-17107 in your dependencies?
Find it across NuGet, including transitive dependencies.