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Unsafe inline XSS in pasting DOM element into chat

High severity GitHub Reviewed Published Sep 26, 2021 in owncast/owncast • Updated Feb 1, 2023

Package

gomod github.com/owncast/owncast (Go)

Affected versions

< 0.0.9

Patched versions

0.0.9

Description

Impact

Inline scripts are executed when Javascript is parsed via a paste action.

  1. Open https://watch.owncast.online/
  2. Copy and then paste <img src=null onerror=alert('hello')> into the
    chat field.
  3. An alert should pop up.

Patches

    ⋮ 13 │    // Content security policy
    ⋮ 14 │    csp := []string{
    ⋮ 15 │        "script-src 'self' 'sha256-2HPCfJIJHnY0NrRDPTOdC7AOSJIcQyNxzUuut3TsYRY='",
    ⋮ 16 │        "worker-src 'self' blob:", // No single quotes around blob:
    ⋮ 17 │    }

Will be 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.

For more information

If you have any questions or comments about this advisory:

References

@gabek gabek published to owncast/owncast Sep 26, 2021
Published by the National Vulnerability Database Dec 14, 2021
Reviewed Dec 14, 2021
Published to the GitHub Advisory Database Dec 14, 2021
Last updated Feb 1, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
High
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:L

EPSS score

0.105%
(45th percentile)

Weaknesses

CVE ID

CVE-2021-39183

GHSA ID

GHSA-2hfj-cxw7-g45p

Source code

Credits

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