GHSA-x462-89pf-6r5h

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GHSA-x462-89pf-6r5h

Summary: Crash due to malformed relay protocol message

Details: ### Impact 1. `syncthing` can be caused to crash and exit if sent a malformed relay protocol message message with a negative length field. 2. The relay server `strelaysrv` can be caused to crash and exit if sent a malformed relay protocol message with a negative length field. At no point is sensitive data exposed or liable to be altered due to this issue. Sensitive data is never exposed to relay operators. Syncthing itself would need to be lured to connect to a malicious relay server in order to exploit the issue. ### Patches Fixed in version 1.15.0. ### Workarounds 1. No known workaround for `strelaysrv`. 2. `syncthing` can be configured to not use relays, or to only use specific, trusted relays. If Syncthing is used in a closed environment or with relaying disabled, i.e., it does not communicate with unknown relays, Syncthing is not vulnerable. ### For more information If you have any questions or comments about this advisory, please discuss it [on the forum](https://forum.syncthing.net/). Thanks to Wojciech Paciorek for discovering and reporting this issue.

References: https://github.com/syncthing/syncthing/security/advisories/GHSA-x462-89pf-6r5h, https://nvd.nist.gov/vuln/detail/CVE-2021-21404, https://github.com/syncthing/syncthing/commit/fb4fdaf4c0a79c22cad000c42ac1394e3ccb6a97, https://github.com/syncthing/syncthing/releases/tag/v1.15.0, https://pkg.go.dev/github.com/syncthing/syncthing