CVE-2026-111367

Description

BillionMail through 4.9 contains a hard-coded cryptographic key vulnerability that allows unauthenticated attackers to forge unsubscribe and subscribe-confirm JWTs by computing the key from shipped configuration constants. Attackers can submit forged tokens to /api/unsubscribe, /api/unsubscribe_new, or /api/subscribe/confirm to deactivate any contact or force confirmed subscriptions.

References

• https://github.com/aaPanel/BillionMail
• https://github.com/aaPanel/BillionMail/blob/v4.9/core/internal/service/batch_mail/jwt.go#L98-L123
• https://github.com/aaPanel/BillionMail/blob/v4.9/core/manifest/config/config.yaml
• https://hackmd.io/@hieuPenguinnn/billionmail-unsubscribe-subscribe-jwt-deterministic-secret-forgery
• https://www.vulncheck.com/advisories/billionmail-through-4.9-forgeable-jwts-via-default-signing-key