punchin-email is a Cloudflare Email Worker that provides two-way role aliases while relaying mail to a private inbox. Prior to 1.5.0, handleInbound delivers inbound alias mail with message.forward(), which silently drops the added Reply-To header intended to route responses through the relay. When a correspondent sends mail to an alias and the operator replies, the mail client can send directly to the correspondent from the private FORWARD_TO inbox address, exposing that address.
The disclosure is limited to the operator's own email address and does not expose third-party data or provide code execution or authentication bypass. This issue is fixed in version 1.5.0.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
Active
User action required
Impact Assessment
Confidentiality
Low
Partial data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
References 4
https://github.com/PunchIn-App/punchin-email/commit/593685ffc0b8eb3949a4838e7bf…
security-advisories@github.com
https://github.com/PunchIn-App/punchin-email/pull/66
security-advisories@github.com
https://github.com/PunchIn-App/punchin-email/releases/tag/v1.5.0
security-advisories@github.com
https://github.com/PunchIn-App/punchin-email/security/advisories/GHSA-2ph7-69xm…
security-advisories@github.com