CVE-2021-39183: Github.com/owncast/owncast Cross-Site Scripting Vulnerability

HIGH
Advisory Identifier: GHSA-2hfj-cxw7-g45p
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CVSS 8.2
CWE-79
Published
Advisory Summary

CVE-2021-39183 is a HIGH (CVSS 8.2) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Github.com/owncast/owncast libraries in the Go ecosystem. The issue involves unsafe inline xss in pasting dom element into chat. Remediation is available by upgrading affected packages to version 0.0.9.

CVE-2021-39183 at a Glance

CVE Identifier CVE-2021-39183
GHSA Identifier GHSA-2hfj-cxw7-g45p
Severity HIGH
CVSS v3.1 Base Score 8.2
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Github.com/owncast/owncast
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 8.2

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity High (I:H)
Availability Low (A:L)

How to Fix CVE-2021-39183

To remediate this vulnerability, upgrade all affected Github.com/owncast/owncast dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/owncast/owncast fixed: 0.0.9 
Upgrade github.com/owncast/owncast to 0.0.9
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/owncast/owncast

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-39183, inspect your project dependencies for Github.com/owncast/owncast:

inspect dependencies for github.com/owncast/owncast

Analyze the terminal output to locate any version of Github.com/owncast/owncast in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.0.9), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Github.com/owncast/owncast, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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: * Open an issue in [owncast/owncast](https://github.com/owncast/owncast/issues) * Email us at [gabek@real-ity.com](mailto:gabek@real-ity.com)

CVE-2021-39183 Affected Github.com/owncast/owncast Versions

1 component(s)
Fixed Versions:
0.0.9
Product / Package Ecosystem Affected Versions Fixed Version
github.com/owncast/owncast
golang/github.com/owncast/owncast
Go
< 0.0.9
0.0.9

References

GitHub Advisory / Wiki ADVISORY
https://github.com/owncast/owncast/security/advisories/GHSA-2hfj-cxw7-g45p
NVD — CVE-2021-39183 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-39183
Github.com/owncast/owncast Source Repository REPOSITORY
https://github.com/owncast/owncast

Frequently Asked Questions

What is CVE-2021-39183?
CVE-2021-39183 is a security vulnerability in Github.com/owncast/owncast involving Unsafe inline XSS in pasting DOM element into chat under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Github.com/owncast/owncast versions are affected?
Affected versions include releases prior to 0.0.9 across affected packages: github.com/owncast/owncast.
What version fixes CVE-2021-39183?
Upgrading to 0.0.9 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/owncast/owncast affected?
Yes, github.com/owncast/owncast is affected in releases prior to 0.0.9. Upgrade your dependency to 0.0.9 or later.
What is the CVSS score of CVE-2021-39183?
CVE-2021-39183 has a CVSS v3.1 base score of 8.2 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:L.
What CWE is associated with CVE-2021-39183?
CVE-2021-39183 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Go dependencies for CVE-2021-39183?
Run the dependency tree command: 'inspect dependencies for github.com/owncast/owncast'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2hfj-cxw7-g45p",
  "modified" : "2022-01-04T18:54:05Z",
  "published" : "2021-12-14T21:48:16Z",
  "aliases" : [ "CVE-2021-39183" ],
  "summary" : "Unsafe inline XSS in pasting DOM element into chat",
  "details" : "### Impact\n\nInline scripts are executed when Javascript is parsed via a paste action.\n\n1. Open https://watch.owncast.online/\n2. Copy and then paste `<img src=null onerror=alert('hello')>` into the\nchat field.\n3. An alert should pop up.\n\n### Patches\n```\n    ⋮ 13 │    // Content security policy\n    ⋮ 14 │    csp := []string{\n    ⋮ 15 │        \"script-src 'self' 'sha256-2HPCfJIJHnY0NrRDPTOdC7AOSJIcQyNxzUuut3TsYRY='\",\n    ⋮ 16 │        \"worker-src 'self' blob:\", // No single quotes around blob:\n    ⋮ 17 │    }\n```\n\nWill 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.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n* Open an issue in [owncast/owncast](https://github.com/owncast/owncast/issues)\n* Email us at [gabek@real-ity.com](mailto:gabek@real-ity.com)\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/owncast/owncast"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.0.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/owncast/owncast/security/advisories/GHSA-2hfj-cxw7-g45p"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-39183"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/owncast/owncast"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-12-14T20:16:10Z",
    "nvd_published_at" : "2021-12-14T20:15:00Z"
  }
}