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CVE-2026-40017

Quick assessment

Affected
Open-Xchange GmbH OX Dovecot Pro
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.

能够向用户发送电子邮件的攻击者可以构造特殊的邮件头，使其在内部哈希表中发生哈希碰撞，从而导致 IMAP 的 命令消耗的 CPU 时间与邮件大小不成比例。这是一个独立于 CVE-2026-40014 的漏洞，且未被该 CVE 的修复所覆盖。当邮件客户端在受影响的邮箱中发起 命令时，可能会导致 IMAP 服务性能下降或服务中断（拒绝服务，DoS）。 缓解措施： 监控系统中的异常 CPU 使用情况； 终止触发问题的进程； 从受影响的邮箱中移除导致问题的邮件； 升级至非易受影响的版本。 目前尚无公开可用的利用方式。

CVSS 6.5 · Medium
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I. Basic Information for CVE-2026-40017

Vulnerability Information
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Vulnerability Title
N/A
Source: CVE Program / CVE List V5
Vulnerability Description
An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Open-Xchange GmbH OX Dovecot Pro 2.3.0 ~ 2.3.22.2 -
Open-Xchange GmbH OX Dovecot CE 2.3.0 ~ 2.4.5 -

II. Public POCs for CVE-2026-40017

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III. Intelligence Information for CVE-2026-40017

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Same Patch Batch · Open-Xchange GmbH · 2026-08-28 · 25 CVEs total

CVE-2026-42007 9.1 CRITICAL OpenWebmail 6.0 及之前版本 内存越界写漏洞
CVE-2026-42391 7.5 HIGH IMAP未认证ID命令引发内存与CPU资源耗尽
CVE-2026-27852 7.5 HIGH Dovecot 特定版本 IMAP 邮件解析内存耗尽 DoS
CVE-2026-33605 7.5 HIGH ManageSieve 认证前畸形命令崩溃DoS漏洞
CVE-2026-40018 7.4 HIGH 未知软件：无已知公开利用
CVE-2026-73208 7.4 HIGH Dovecot OAuth2 audience 冒充 scope 导致越权
CVE-2026-52687 6.5 MEDIUM Dovecot IMAP压缩算法致拒绝服务
CVE-2026-40014 6.5 MEDIUM IMAP THREAD命令致高CPU占用，修复指定版本
CVE-2026-73209 6.5 MEDIUM IMAP服务栈溢出拒绝服务漏洞
CVE-2026-33604 5.9 MEDIUM Dovecot SMTP邮件走私漏洞
CVE-2026-40019 5.9 MEDIUM ManageSieve 0.6.1 存在 CPU 耗尽型拒绝服务漏洞
CVE-2026-40205 5.9 MEDIUM OAuth2 令牌校验缺陷，远程验证未强制作用域
CVE-2026-33606 4.8 MEDIUM Dovecot dsync流协议邮件内容注入漏洞
CVE-2026-42008 4.3 MEDIUM Dovecot 受信代理认证字段注入漏洞
CVE-2026-33607 4.3 MEDIUM IMAP LIST命令致CPU耗尽或DoS
CVE-2026-33263 4.3 MEDIUM 提交登录模块崩溃：高并发下连接上限触发 epoll 异常
CVE-2026-40015 4.3 MEDIUM IMAP-hibernate越界读致进程崩溃
CVE-2026-40013 4.3 MEDIUM ManageSieve 越界写导致拒绝服务漏洞
CVE-2026-42392 4.3 MEDIUM 该漏洞影响某软件的IMAP URLAUTH功能，版本未知，类型为信息泄露
CVE-2026-42395 4.3 MEDIUM OpenSSH可信代理NUL字节致登录进程崩溃

Showing top 20 of 25 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: OX Dovecot Pro
Same vendor: Open-Xchange GmbH
Same weakness: CWE-400

V. Comments for CVE-2026-40017

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