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.
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Fri, 28 Aug 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 28 Aug 2026 14:00:00 +0000

Type Values Removed Values Added
Title IMAP Compression Reuse Allows Recipient‑Dependent Information Disclosure

Fri, 28 Aug 2026 11:30:00 +0000

Type Values Removed Values Added
Description 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.
Weaknesses CWE-200
References
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: OX

Published:

Updated: 2026-08-28T14:57:07.686Z

Reserved: 2026-04-10T07:11:39.060Z

Link: CVE-2026-40203

cve-icon Vulnrichment

Updated: 2026-08-28T14:57:03.836Z

cve-icon NVD

Status : Received

Published: 2026-08-28T12:16:28.897

Modified: 2026-08-28T16:17:57.233

Link: CVE-2026-40203

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-28T13:45:17Z

Weaknesses