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CVE-2026-107566— Missing Authorization in hMailServer

Quick assessment

Affected
Progressive Robot Ltd hMailServer
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.

Progressive Robot hMailServer 在 6.2.22 至 6.3.6 版本的 Sieve 动作中,以及在 6.0.0 至 6.3.6 版本的邮件规则“设置标头值”动作中,存在授权缺失漏洞。该漏洞允许已认证用户使服务器以任意邮箱地址发送邮件;若该地址属于服务器已启用 DKIM 签名的域名,则邮件可被服务器以该域名的 DKIM 密钥签名。 具体而言,Sieve 脚本的 (含 / )操作可添加或删除除 和 之外的任意邮件标头字段。由于服务器在将重定向邮件入队前即应用脚本对标头的修改,因此重定向副本

CVSS 6.5 · Medium

Affected Version Matrix 1

VendorProduct Version RangeStatus
Progressive Robot Ltd hMailServer 6.0.0≤ 6.3.6 affected
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I. Basic Information for CVE-2026-107566

Vulnerability Information

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Vulnerability Title
Missing Authorization in hMailServer
Source: CVE Program / CVE List V5
Vulnerability Description
Missing authorization in the Sieve editheader action (6.2.22 through 6.3.6) and in the mail-rule Set header value action (6.0.0 through 6.3.6) of Progressive Robot hMailServer allows an authenticated user to make the server send mail as any address, DKIM-signed where the address is at a domain the server signs for. A Sieve script's editheader (addheader/deleteheader) could add or delete any header field except Received and Return-Path, and the server applies a script's header edits before it queues a redirect, so the redirected copy is sent as the script left it. The server signs a message's first delivery pass as the domain named in its From header wherever it signs DKIM for that domain and the message carries no signature of it. A script could therefore delete and re-add From - another account's address, or anyone's at a hosted domain - and redirect, so the server sent the message in that name and, for a hosted domain, signed it with that domain's DKIM key, a forgery aligned to pass the domain's DMARC; or, where another sender's domain is one the server signs for, delete the DKIM-Signature that sender's message arrived with, alter a field, and redirect, so the server re-signed the altered message as that sender's domain. editheader placed no restriction on From, Sender, Resent-From, Resent-Sender or DKIM-Signature. The editheader action was introduced in 6.2.22. In the mail-rule engine, a domain's or an account's rule's Set header value action could likewise set From, Sender, Resent-From, Resent-Sender or DKIM-Signature ahead of a forward or a copy, whoever the rule belonged to, so that an account acting on its own rules over COM, a domain administrator, or an API key confined to a domain (over the REST API from 6.3.4) could have the server forward or copy a message in the name of any address, signed, where that address is at a domain the server hosts with DKIM signing enabled, with that domain's key.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Progressive Robot Ltd hMailServer 6.0.0 ~ 6.3.6 -

II. Public POCs for CVE-2026-107566

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III. Intelligence Information for CVE-2026-107566

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Other References for CVE-2026-107566 (2)

Same Patch Batch · Progressive Robot Ltd · 2026-10-19 · 5 CVEs total

CVE-2026-107571 7.8 HIGH Incorrect Default Permissions in hMailServer
CVE-2026-107567 7.5 HIGH Use of Less Trusted Source in hMailServer
CVE-2026-107569 7.5 HIGH Unchecked Input for Loop Condition in hMailServer
CVE-2026-107568 6.5 MEDIUM Missing Authorization in hMailServer

IV. Related Vulnerabilities

V. Comments for CVE-2026-107566

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