Neko: Authorization bypass in legacy WebRTC input handling

### Impact When legacy mode is enabled and `session.implicit_hosting` is enabled, the legacy WebRTC data channel incorrectly authorizes input events due to a logic error in `LegacyIsHost()`. As a result, an authenticated room member may be able to send mouse and keyboard input through the legacy WebRTC control channel even when controls are locked or the member would otherwise not be authorized through the modern control API. The issue affects only the legacy WebRTC input path. The modern HTTP/WebSocket control path correctly enforces authorization checks and is not affected. To exploit this issue, an attacker must: * Be authenticated as a room member. * Successfully establish a WebRTC connection. * Access a deployment using the legacy WebRTC input handler. No unauthenticated access or privilege escalation outside the application is possible. ### Patches The issue has been fixed in **[v3.1.5](https://github.com/m1k1o/neko/releases/tag/v3.1.5)** by correcting the authorization logic in the legacy WebRTC handler. Users should upgrade to **[v3.1.5](https://github.com/m1k1o/neko/releases/tag/v3.1.5)** or later. Fix: *[395ca1a](https://github.com/m1k1o/neko/commit/395ca1a6f62b7b0e270e654d366a2d57b8042efd)* ### Workarounds Users who cannot immediately upgrade can mitigate the issue by one of the following: * Disable legacy mode if it is not required. * Disable implicit hosting (`session.implicit_hosting=false`). * Restrict access to trusted authenticated users. ### Credits Thanks to @KasperBuilds for responsibly disclosing this vulnerability and reaching out directly. This contribution helped strengthen the project, and the whole community benefits from it.

Source published

27 Oct 2026 21:04:57 UTC

Source modified

27 Oct 2026 21:15:03 UTC

Observed here

27 Oct 2026 21:48:52 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Publisher rating · MODERATE