CVE-2026-103647 Progressive Robot hMailServer - Stored XSS

Progressive Robot hMailServer 6.3.2 through 6.3.5 contains a stored XSS caused by unsafe rendering of decrypted S/MIME or OpenPGP message attachments as blob URLs in webmail, letting remote attackers execute scripts in the user's session, exploit requires REST API enabled.

CVSS base score 8.0 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.25% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Stored XSS
Impact
Stored XSS, Information Disclosure, Data Tampering
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
Published
8 October 2026
Updated
15 October 2026
Weakness
CWE-79

Vendor fix

Update to a version later than 6.3.5 or apply vendor patches.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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