CVE-2026-33606: CRLF Injection
Mail content stored by a user can be crafted so that it is interpreted as dsync protocol commands when an administrator later runs dsync with the stream protocol, for example during a migration. Injected commands can modify mailbox state on the destination during migration or replication, including internal mailbox attributes that a user should not be able to set directly. It can also cause dsync errors. Avoid running dsync with the stream protocol on mailboxes with untrusted content. Update to non-vulnerable version. No publicly available exploits are known.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Avoid running dsync with the stream protocol on mailboxes with untrusted content to prevent crafted mailbox content from being interpreted as dsync protocol commands during later migrations/replication.
dsync use stream protocol = disable when mailboxes contain untrusted content
Event History
Frequently Asked Questions
Who is exposed to this issue?
Organizations that run dsync with the stream protocol on mailboxes containing untrusted user-controlled mail content are exposed. The issue is relevant when an administrator later uses that protocol for migration or replication.
What does an attacker need to do to exploit it?
An attacker needs the ability to store specially crafted mail content in a mailbox. Exploitation also requires an administrator to run dsync using the stream protocol against that mailbox.
What is the impact of successful exploitation?
Injected content can be interpreted as dsync commands and modify mailbox state on the destination system during migration or replication. This can include internal mailbox attributes that users normally cannot set directly, and can also trigger dsync errors.
What can be done if an update cannot be applied immediately?
Avoid running dsync with the stream protocol on mailboxes that contain untrusted content. Update to a non-vulnerable version when possible.
Are public exploits available?
No publicly available exploits are known.