CVE-2026-103647 json
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in hMailServer
published last mo. modified last mo. also EUVD-2026-94836
- cvss
- 8.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 16%
- public exploits
- 0
- none known
Summary
Cross-site scripting in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5 allows a remote attacker who can send a user an encrypted message to run script in the webmail's origin with that user's session. When the webmail decrypted an S/MIME message (from 6.3.2) or an OpenPGP message (from 6.3.4) in the browser, it offered each decrypted attachment as a blob URL of the media type the message declared for it. A click saved the file, but if the user opened the attachment in a new tab, a part declared as text/html was rendered as a document of the webmail's origin and its script could read the mailbox, send mail and change the account through the REST API. The webmail is served only when the REST API is enabled, which it is not by default.
Patch / fix
- Progressive Robot Ltd hMailServer 6.3.6
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- last mo.
Exploit prediction
0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N |
Affected products
- Progressive Robot Ltd hMailServer
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
Sources
- CVE List CVE-2026-103647
- NVD CVE-2026-103647
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