Summary
tgstation-server cached user logins in legacy server
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+
Impact
CVE-2018-17107 has a CVSS score of 8.3 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.2.5.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Frequently Asked Questions
- What is CVE-2018-17107? CVE-2018-17107 is a high-severity security vulnerability in TGServiceInterface (nuget), affecting versions >= 3.2.1.0, <= 3.2.4.0. It is fixed in 3.2.5.0.
- How severe is CVE-2018-17107? CVE-2018-17107 has a CVSS score of 8.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of TGServiceInterface are affected by CVE-2018-17107? TGServiceInterface (nuget) versions >= 3.2.1.0, <= 3.2.4.0 is affected.
- Is there a fix for CVE-2018-17107? Yes. CVE-2018-17107 is fixed in 3.2.5.0. Upgrade to this version or later.
- Is CVE-2018-17107 exploitable, and should I be worried? Whether CVE-2018-17107 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2018-17107 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2018-17107? Upgrade
TGServiceInterfaceto 3.2.5.0 or later.