VULNERABILITY INTELLIGENCE
CVE-2026-40203
CVSS score3.7 LOW
EPSS probability0.26%
CISA KEVNot currently listed
Published2026-08-28
Last modified2026-09-03
CVSS vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
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.
Weakness classification
- security@open-xchange.com: CWE-200