GHSA-3CRJ-W4F5-GWH4

Vulnerability from github – Published: 2021-01-29 20:51 – Updated: 2021-02-16 17:35
VLAI
Summary
Processing untrusted theming resources might execute arbitrary code (ACE)
Details

Impact

When processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process.

While this is a feature of the Less.js library, it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development.

Especially in the context of UI5 Tooling, which relies on less-openui5, this poses a security threat:

An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files.

This is an example of inline JavaScript in a Less file:

.rule {
    @var: `(function(){console.log('Hello from JavaScript'); process.exit(1);})()`;
    color: @var;
}

Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3.

Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it:

.rule {
    @var: "`(function(){console.log('Hello from JavaScript'); process.exit(1);})()`";
    color: @var;
}

Patches

We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork.

This fix is available in less-openui5 version v0.10.0

Workarounds

Only process trusted theming resources.

For more information

If you have any questions or comments about this advisory: * Open an issue in https://github.com/SAP/less-openui5 * Email us at secure@sap.com

Severity
6.3 (Medium)
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "less-openui5"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2021-21316"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-74"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2021-01-29T20:50:46Z",
    "nvd_published_at": "2021-02-16T18:15:00Z",
    "severity": "HIGH"
  },
  "details": "### Impact\nWhen processing theming resources (i.e. `*.less` files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process.\n\nWhile this is a [feature](http://lesscss.org/usage/#less-options-enable-inline-javascript-deprecated-) of the [Less.js library](https://github.com/less/less.js), it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development.\n\nEspecially in the context of [UI5 Tooling](https://github.com/SAP/ui5-tooling), which relies on less-openui5, this poses a security threat:\n\nAn attacker might create a [library](https://sap.github.io/ui5-tooling/pages/Builder/#library) or [theme-library](https://sap.github.io/ui5-tooling/pages/Builder/#theme-library) containing a custom control or theme, hiding malicious JavaScript code in one of the `.less` files.\n\nThis is an example of inline JavaScript in a Less file:\n```less\n.rule {\n\t@var: `(function(){console.log(\u0027Hello from JavaScript\u0027); process.exit(1);})()`;\n\tcolor: @var;\n}\n```\n\nStarting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses [a fork](https://github.com/SAP/less-openui5/tree/master/lib/thirdparty/less) of Less.js v1.6.3.\n\nNote that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it:\n```less\n.rule {\n\t@var: \"`(function(){console.log(\u0027Hello from JavaScript\u0027); process.exit(1);})()`\";\n\tcolor: @var;\n}\n```\n\n### Patches\nWe decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork.\n\nThis fix is available in less-openui5 version [v0.10.0](https://github.com/SAP/less-openui5/releases/tag/v0.10.0)\n\n### Workarounds\nOnly process trusted theming resources.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in https://github.com/SAP/less-openui5\n* Email us at secure@sap.com",
  "id": "GHSA-3crj-w4f5-gwh4",
  "modified": "2021-02-16T17:35:25Z",
  "published": "2021-01-29T20:51:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/SAP/less-openui5/security/advisories/GHSA-3crj-w4f5-gwh4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-21316"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SAP/less-openui5/commit/c0d3a8572974a20ea6cee42da11c614a54f100e8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SAP/less-openui5/releases/tag/v0.10.0"
    },
    {
      "type": "WEB",
      "url": "https://www.npmjs.com/package/less-openui5"
    },
    {
      "type": "WEB",
      "url": "http://lesscss.org/usage/#less-options-enable-inline-javascript-deprecated-"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Processing untrusted theming resources might execute arbitrary code (ACE)"
}



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