GHSA-P4X4-RW2P-8J8M

Vulnerability from github – Published: 2020-06-16 22:08 – Updated: 2023-05-16 16:18
VLAI?
Summary
Cross-site Scripting in Sanitize
Details

When HTML is sanitized using Sanitize's "relaxed" config or a custom config that allows certain elements, some content in a <math> or <svg> element may not be sanitized correctly even if math and svg are not in the allowlist.

You are likely to be vulnerable to this issue if you use Sanitize's relaxed config or a custom config that allows one or more of the following HTML elements:

  • iframe
  • math
  • noembed
  • noframes
  • noscript
  • plaintext
  • script
  • style
  • svg
  • xmp

Impact

Using carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize, potentially resulting in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser.

Releases

This problem has been fixed in Sanitize 5.2.1.

Workarounds

If upgrading is not possible, a workaround is to override the default value of Sanitize's :remove_contents config option with the following value, which ensures that the contents of math and svg elements (among others) are removed entirely when those elements are not in the allowlist:

%w[iframe math noembed noframes noscript plaintext script style svg xmp]

For example, if you currently use Sanitize's relaxed config, you can create a custom config object that overrides the default value of :remove_contents like this:

custom_config = Sanitize::Config.merge(
  Sanitize::Config::RELAXED,
  :remove_contents => %w[iframe math noembed noframes noscript plaintext script style svg xmp]
)

You would then pass this custom config to Sanitize when sanitizing HTML.

For more information

If you have any questions or comments about this advisory:

Credits

Many thanks to Michal Bentkowski of Securitum for reporting this bug and helping to verify the fix.

References

Severity ?
7.3 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "sanitize"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "5.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2020-4054"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2020-06-16T21:42:41Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "When HTML is sanitized using Sanitize\u0027s \"relaxed\" config or a custom config that allows certain elements, some content in a `\u003cmath\u003e` or `\u003csvg\u003e` element may not be sanitized correctly even if `math` and `svg` are not in the allowlist.\n\nYou are likely to be vulnerable to this issue if you use Sanitize\u0027s relaxed config or a custom config that allows one or more of the following HTML elements:\n\n- `iframe`\n- `math`\n- `noembed`\n- `noframes`\n- `noscript`\n- `plaintext`\n- `script`\n- `style`\n- `svg`\n- `xmp`\n\n### Impact\n\nUsing carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize, potentially resulting in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser.\n\n### Releases\n\nThis problem has been fixed in Sanitize 5.2.1.\n\n### Workarounds\n\nIf upgrading is not possible, a workaround is to override the default value of Sanitize\u0027s `:remove_contents` config option with the following value, which ensures that the contents of `math` and `svg` elements (among others) are removed entirely when those elements are not in the allowlist:\n\n```ruby\n%w[iframe math noembed noframes noscript plaintext script style svg xmp]\n```\n\nFor example, if you currently use Sanitize\u0027s relaxed config, you can create a custom config object that overrides the default value of `:remove_contents` like this:\n\n```ruby\ncustom_config = Sanitize::Config.merge(\n  Sanitize::Config::RELAXED,\n  :remove_contents =\u003e %w[iframe math noembed noframes noscript plaintext script style svg xmp]\n)\n```\n\nYou would then pass this custom config to Sanitize when sanitizing HTML.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n\n- Open an issue in the [Sanitize repo](https://github.com/rgrove/sanitize).\n- See Sanitize\u0027s [security policy](https://github.com/rgrove/sanitize/security/policy).\n\n### Credits\n\nMany thanks to Michal Bentkowski of Securitum for reporting this bug and helping to verify the fix.\n\n### References\n\n- [GHSA-p4x4-rw2p-8j8m](https://github.com/rgrove/sanitize/security/advisories/GHSA-p4x4-rw2p-8j8m)\n- [CVE-2020-4054](https://nvd.nist.gov/vuln/detail/CVE-2020-4054)\n- https://github.com/rgrove/sanitize/releases/tag/v5.2.1",
  "id": "GHSA-p4x4-rw2p-8j8m",
  "modified": "2023-05-16T16:18:26Z",
  "published": "2020-06-16T22:08:06Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/rgrove/sanitize/security/advisories/GHSA-p4x4-rw2p-8j8m"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-4054"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rgrove/sanitize/commit/a11498de9e283cd457b35ee252983662f7452aa9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rgrove/sanitize"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rgrove/sanitize/releases/tag/v5.2.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/sanitize/CVE-2020-4054.yml"
    },
    {
      "type": "WEB",
      "url": "https://usn.ubuntu.com/4543-1"
    },
    {
      "type": "WEB",
      "url": "https://www.debian.org/security/2020/dsa-4730"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Cross-site Scripting in Sanitize "
}


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