CVE intelligence and bounded remediation

CVE-2026-33368 — Synacor Zimbra Collaboration Suite security vulnerability

Medium CVSS 6.1

Zimbra Collaboration Suite (ZCS) 10.0 and 10.1 contains a reflected cross-site scripting (XSS) vulnerability in the Classic Webmail REST interface (/h/rest). The application fails to properly sanitize user-supplied input, allowing an unauthenticated attacker to inject malicious JavaScript into a crafted URL. When a victim user accesses the link, the injected script executes in the context of the Zimbra webmail application, which could allow the attacker to perform actions on behalf of the victim.

Severity
Medium
CVSS
6.1 (3.1)
Published
2026-03-20
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-79

Affected products

  • synacor / zimbra_collaboration_suite

Matched remediation archetype

Cross-site scripting and unsafe browser output

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace reflected, stored, and DOM-derived untrusted values into HTML, attributes, URLs, styles, scripts, and client-side template sinks.
  • Identify affected origins, authenticated user roles, sensitive browser capabilities, and where content is shared across tenants.
  • Review framework escaping, rich-text sanitization, legacy templates, and client-side rendering paths.

Remediate safely

  • Use context-aware framework output encoding and safe DOM APIs; keep untrusted data out of executable contexts.
  • Sanitize intentionally supported markup with a maintained allowlist policy and validate URLs and attributes separately.
  • Update affected rendering components and add tests for every output context using inert sentinel markup.

Authoritative sources

Complete CVE record and remediation plan

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