{"id":"CVE-2021-21316","aliases":["GHSA-3crj-w4f5-gwh4"],"url":"https://o3.security/vulnerability/CVE-2021-21316","summary":"Processing untrusted theming resources might execute arbitrary code (ACE)","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('Hello from JavaScript'); 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('Hello from JavaScript'); 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","published":"2021-02-16T18:15:12.490Z","modified":"2026-07-09T10:52:42.285438Z","cvss":{"score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"less-openui5","fixedVersion":"0.10.0"}],"fix":{"url":"https://github.com/SAP/less-openui5/commit/c0d3a8572974a20ea6cee42da11c614a54f100e8","label":"SAP/less-openui5@c0d3a85"},"references":[{"type":"ADVISORY","url":"http://lesscss.org/usage/#less-options-enable-inline-javascript-deprecated-"},{"type":"ADVISORY","url":"https://github.com/SAP/less-openui5/releases/tag/v0.10.0"},{"type":"ADVISORY","url":"https://github.com/SAP/less-openui5/security/advisories/GHSA-3crj-w4f5-gwh4"},{"type":"ADVISORY","url":"https://www.npmjs.com/package/less-openui5"},{"type":"FIX","url":"https://github.com/SAP/less-openui5/commit/c0d3a8572974a20ea6cee42da11c614a54f100e8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21316"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T10:52:42.285438Z"}}