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CVE-2026-61911

Quick assessment

Affected
cyrusimap Cyrus IMAP
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Cyrus IMAP 在 3.12.4 之前的版本中存在一个安全问题：存在一个“Sieve 邮箱存在性预言机”（Sieve mailbox existence oracle）。一个经过认证的用户可以安装一个 Sieve 脚本，通过观察 LMTP 投递过程中哪个 分支被触发，来探测其他用户的私有邮箱是否存在，或者读取共享邮箱的注释（annotations）值。

CVSS 4.3 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-61911

Vulnerability Information
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Vulnerability Title
N/A
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
将系统数据暴露到未授权控制的范围
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
cyrusimap Cyrus IMAP 0 ~ 3.8.8 -

II. Public POCs for CVE-2026-61911

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III. Intelligence Information for CVE-2026-61911

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Vendor Pages for CVE-2026-61911 (4)

Same Patch Batch · cyrusimap · 2026-09-09 · 6 CVEs total

CVE-2026-61907 4.3 MEDIUM Cyrus IMAP 3.12.4前JMAP Snooze ACL绕过
CVE-2026-61915 4.2 MEDIUM Cyrus IMAP 3.12.4前 认证用户致CalDAV进程崩溃
CVE-2026-61910 3.5 LOW Cyrus IMAP 3.12.4前共享邮箱权限控制缺陷
CVE-2026-61909 3.5 LOW Cyrus IMAP 3.12.4前 CalDAV多获取ACL绕过
CVE-2026-61908 3.1 LOW Cyrus IMAP<3.12.4 JMAP越界读堆内存

IV. Related Vulnerabilities

Same product: Cyrus IMAP
Same vendor: cyrusimap
Same weakness: CWE-497

V. Comments for CVE-2026-61911

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