---
id: CVE-2026-61911
title: An issue was discovered in Cyrus IMAP before 3.12.4
summary: >-
  An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox
  existence oracle. An authenticated user could install a Sieve script that
  probed whether another user's private mailbox existed, or read the value of
  shared ma…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-497
vendor: cyrus
product: imap
affected:
  - imap < 3.8.8
  - 'imap >= 3.9.0, < 3.10.4'
  - 'imap >= 3.11.0, < 3.12.4'
patched:
  - imap 3.12.4
published: '2026-09-09'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T15:23:58.500'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-61911'
references:
  - url: 'https://cyrusimap.org'
    label: cve@mitre.org
  - url: >-
      https://www.cyrusimap.org/3.12/imap/download/release-notes/3.10/x/3.10.4.html
    label: cve@mitre.org
  - url: >-
      https://www.cyrusimap.org/3.12/imap/download/release-notes/3.12/x/3.12.4.html
    label: cve@mitre.org
  - url: >-
      https://www.cyrusimap.org/3.12/imap/download/release-notes/3.8/x/3.8.8.html
    label: cve@mitre.org
tags:
  - nvd
  - cve.org
epss: 0.00373
epssPercentile: 0.2852
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-10T18:59:21.694757Z'
ingestedAt: '2026-09-11T17:50:33.677Z'
---

## Overview

An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence oracle. An authenticated user could install a Sieve script that probed whether another user's private mailbox existed, or read the value of shared mailbox annotations, by observing which fileinto branch fired during LMTP delivery.

## Affected

- `imap < 3.8.8`
- `imap >= 3.9.0, < 3.10.4`
- `imap >= 3.11.0, < 3.12.4`

## Remediation

Upgrade past the affected range:

- `imap 3.12.4`