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  4. CVE 2026 103647 improper neutralization of input during web page
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Back to active CVEs
High · CVSS 8.0CVE-2026-103647

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in hMailServerCVE-2026-103647

Answer in brief

CVE-2026-103647 records a High severity (CVSS 8.0) vulnerability in Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in hMailServer. The current sources do not mark it as known exploited. The current feed maps Progressive Robot Ltd/hMailServer (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 8, 2026Updated Oct 8, 2026Source checked Oct 8, 2026First seen by HOL Oct 8, 2026Material review Oct 8, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 8.0
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 8.0. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Progressive Robot Ltd/hMailServer (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Progressive Robot Ltd/hMailServergeneric>=6.3.2 <6.3.66.3.6

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Progressive Robot Ltd/hMailServer.
  2. 2Review the reported fix. Source-reported solution: Upgrade to hMailServer 6.3.6, which hands every decrypted attachment to the browser as application/octet-stream so that it is only ever saved. Until then: keep the REST API off (RestApiPort 0, the default), or tell webmail users not to open decrypted attachments in a new tab.

Evidence timeline and material changes

  1. Published upstream

    Oct 8, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 8, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 8, 2026

Sources and claim methodology

  • Source referencegitlab.com
  • Source referencegitlab.com
Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • Heap-based Buffer Overflow in hMailServerSame progressive robot ltd/hmailserver package
  • Heap-based Buffer Overflow in hMailServerSame progressive robot ltd/hmailserver package
  • Synchronous Access of Remote Resource without Timeout in hMailServerSame progressive robot ltd/hmailserver package
  • Reliance on Untrusted Inputs in a Security Decision in hMailServerSame progressive robot ltd/hmailserver package
  • Origin Validation Error in hMailServerSame progressive robot ltd/hmailserver package
  • Missing Authorization in hMailServerSame progressive robot ltd/hmailserver package

Record context

Vulnerability class
XSS
EPSS
Not reported
CWE IDs
CWE-79
Source
CVE List V5
Source checked
Oct 8, 2026
References
2 linked sources
Open source record