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CVE-2026-40203

When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attac

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 2.3.22.2, 3.0.7, 3.1.6, 2.4.5
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. Disable IMAP compression. Update to non-vulnerable version. No publicly available exploits are known.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • 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

References 1

documentation.open-xchange.com