Description

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.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.8",
  "pubDate": "2026-08-28T12:16:27.867Z",
  "pubdate": "2026-08-28T12:16:27.867Z",
  "executiveSummary": "A command injection vulnerability exists within the dsync protocol implementation, specifically when utilizing the stream protocol. This flaw allows a malicious user to craft mailbox content that, when processed by administrative dsync operations, is misinterpreted as valid dsync commands. The vulnerability affects systems where administrators perform migrations or replications of untrusted mailbox data. Successful exploitation enables an attacker to manipulate the state of mailboxes on a destination server, modify internal mailbox attributes that are typically restricted from user access, and induce service-level errors. The primary risk involves unauthorized modification of mailbox metadata and potential escalation of control during the synchronization process. Exploitation requires the attacker to have existing access to write content into a mailbox that is subsequently processed by an administrator via the vulnerable stream protocol. No publicly known exploits currently exist, but the nature of the flaw poses a significant integrity risk to migrated mail environments.",
  "technicalDetails": "The vulnerability originates from a failure to properly sanitize mailbox content data when processed by the dsync tool using the stream protocol. The dsync stream protocol relies on a structured command format to synchronize mailbox states between server instances. However, the parser responsible for interpreting these streams does not adequately distinguish between legitimate administrative protocol commands and data stored within the mailbox that mimics these commands.\nThe exploitation flow initiates when an authenticated user injects specially crafted data into their mailbox content. This data acts as a payload designed to conform to the syntax of dsync protocol commands. When an administrator initiates a migration or replication task, the dsync process reads this malicious content from the source mailbox and streams it to the destination. Because the input validation logic is insufficient, the dsync process on the destination server treats the injected content as part of the command stream rather than as passive message data.\nThe impact of this injection allows for the modification of sensitive mailbox state information on the destination system. Specifically, an attacker can manipulate internal mailbox attributes that are intended to be managed exclusively by the system or authorized administrators. By forcing the destination dsync instance to execute injected commands, the attacker can alter metadata, flags, or other storage-level properties that would otherwise be protected by access control lists or privilege boundaries. Furthermore, the injection can be used to intentionally trigger protocol-level errors within dsync, potentially leading to a denial-of-service condition for the specific synchronization task or destabilizing the migration process.\nThe root cause is a trust boundary violation where untrusted mailbox content is allowed to influence the instruction set of the dsync stream protocol parser. The vulnerability is inherent to the parsing logic of the stream protocol implementation. Mitigation is complicated by the nature of the data flow, as the protocol assumes that all content passed during migration is implicitly trusted administrative traffic. As such, the attack does not require network-level authentication by the attacker during the migration phase, as the malicious payload is pre-positioned within the storage environment, awaiting administrative action to be executed."
}