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CVE-2026-104660— 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.

在 Progressive Robot hMailServer 6.0.0 至 6.3.5 版本（仅限 Windows）中，COM 对象存在授权缺失漏洞，允许任何本地交互式用户（无需 hMailServer 凭据）以服务账户身份读写任意文件，并伪造任意发件人发送电子邮件。 该服务在注册其 COM 类时未设置 DCOM 访问权限或启动权限，并调用 而未指定安全描述符。因此，任何通过控制台或远程桌面（RDP）登录系统的用户，均可激活运行中服务内的 COM 类。通过这种方式创建的 对象、其 和 对象，以及 对象，均携带从

CVSS 7.8 · High
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I. Basic Information for CVE-2026-104660

Vulnerability Information
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Vulnerability Title
Missing Authorization in hMailServer
Source: CVE Program / CVE List V5
Vulnerability Description
Missing authorization on COM objects in Progressive Robot hMailServer 6.0.0 through 6.3.5 (Windows only) lets a local interactive user with no hMailServer credential read and write arbitrary files as the service account and queue mail as any sender. The service registers its COM classes with no DCOM access or launch permission and calls CoInitializeSecurity with no security descriptor, so any user logged on at the console or over Remote Desktop can activate the classes in the running service; a hMailServer.Message, its Attachments and Attachment, and a hMailServer.FetchAccount created this way carry a credential that never authenticated. Attachments.Add(path) and Attachment.SaveAs(path) performed no authorization check, and Message.Save/Copy and FetchAccount.AccountID/Save performed none either up to 6.3.3 and from 6.3.4 treated a holder with no credential as the server's own event-script host. Because the service does not impersonate the COM caller, Attachments.Add reads any file the service account can read and returns it, Attachment.SaveAs writes attacker-chosen bytes to any path it can write (on a LocalSystem installation, code execution as SYSTEM), Message.Save queues outbound mail from any address past the SMTP checks, and FetchAccount attaches a mail-fetch job to any mailbox. The objects an Application handed out behave the same once a later Authenticate on that Application fails.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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-2026-104660

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III. Intelligence Information for CVE-2026-104660

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Other References for CVE-2026-104660 (2)

Same Patch Batch · Progressive Robot Ltd · 2026-10-08 · 22 CVEs total

CVE-2026-103647 8.0 HIGH Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in hM
CVE-2026-103010 7.8 HIGH Heap-based Buffer Overflow in hMailServer
CVE-2026-107573 7.8 HIGH Incorrect Default Permissions in hMailServer
CVE-2026-104658 7.8 HIGH Reliance on Untrusted Inputs in a Security Decision in hMailServer
CVE-2026-103649 7.5 HIGH Synchronous Access of Remote Resource without Timeout in hMailServer
CVE-2026-107577 7.5 HIGH Loop with Unreachable Exit Condition ('Infinite Loop') in hMailServer
CVE-2026-107574 7.5 HIGH Inefficient Algorithmic Complexity in hMailServer
CVE-2026-107579 7.5 HIGH Inefficient Algorithmic Complexity in hMailServer
CVE-2026-107576 7.5 HIGH Inefficient Algorithmic Complexity in hMailServer
CVE-2026-104659 7.5 HIGH Origin Validation Error in hMailServer
CVE-2026-107584 7.4 HIGH Not Failing Securely ('Failing Open') in hMailServer
CVE-2026-104704 7.4 HIGH Cleartext Transmission of Sensitive Information in hMailServer
CVE-2026-107578 6.7 MEDIUM Improper Link Resolution Before File Access ('Link Following') in hMailServer
CVE-2026-103011 6.5 MEDIUM Heap-based Buffer Overflow in hMailServer
CVE-2026-107583 6.5 MEDIUM Inefficient Algorithmic Complexity in hMailServer
CVE-2026-107572 6.5 MEDIUM Inefficient Regular Expression Complexity in hMailServer
CVE-2026-107581 6.5 MEDIUM Inefficient Algorithmic Complexity in hMailServer
CVE-2026-107582 6.5 MEDIUM Inefficient Algorithmic Complexity in hMailServer
CVE-2026-107580 6.5 MEDIUM Inefficient Algorithmic Complexity in hMailServer
CVE-2026-107587 5.9 MEDIUM Improper Certificate Validation in hMailServer

Showing top 20 of 22 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: hMailServer
Same vendor: Progressive Robot Ltd
Same weakness: CWE-862

V. Comments for CVE-2026-104660

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