CVE intelligence and bounded remediation

CVE-2021-39183 — Owncast is an open source, self-hosted live video streaming and chat server

High CVSS 8.2

Owncast is an open source, self-hosted live video streaming and chat server. In affected versions inline scripts are executed when Javascript is parsed via a paste action. This issue is patched in 0.0.9 by blocking unsafe-inline Content Security Policy and specifying the script-src. The worker-src is required to be set to blob for the video player.

Severity
High
CVSS
8.2 (3.1)
Published
2021-12-14
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-79

Affected products

  • owncast_project / owncast

Matched remediation archetype

Cross-site scripting and unsafe browser output

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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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