Vulnerability in mlogclub bbs-go

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

bbs-go through 4.4.6 contains an authentication bypass vulnerability in the /api/login/google_one_tap endpoint that allows remote attackers to log in as other users by submitting Google ID tokens issued to any OAuth client. Attackers operating their own Google OAuth client can capture a victim's Google-signed ID token and replay it, since the aud claim is never checked, to obtain an authenticated session as the victim's Google-linked account.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ References ]References

• github.com/mlogclub/bbs-go/blob/v4.4.6/internal/pkg/google/jwt.go
• github.com/mlogclub/bbs-go/blob/v4.4.6/internal/services/third_user_service.go
• hackmd.io/@hieuPenguinnn/bbs-go-google-one-tap-id-token-audience-confusion-account-take…
• www.vulncheck.com/advisories/bbs-go-through-4.4.6-account-takeover-via-google-one-tap-l…