GHSA-xwwr-4h3p-r22c: rclone serve s3: --auth-proxy without --auth-key authenticates nobody - full SigV4 signature bypass
HIGHCritical vulnerability — CVSS 9.8
What to do
- Critical severity — schedule an urgent patch.
### Summary `rclone serve s3`'s handler chain, when `--auth-proxy` is configured, is (outermost first): `authPairMiddleware` -> `proxyAuthMiddleware` -> gofakes3's own SigV4-verifying handler. `authPairMiddleware` parses the accessKeyID straight out of the incoming request's own `Authorization` header (entirely client-controlled) and registers `{accessKey: ws.s3Secret}` into gofakes3's shared credential store via `AddAuthKeys`, for EVERY access key any client presents - not just ones previously known to the server. …
CVE · detail
- CVE-2026-88018nvd ↗EPSS 0.50%
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