{"id":"GHSA-9wx9-5pv9-3349","summary":"Seroval: Script injection through RegExp sources in serialized output","details":"### Summary\n\nseroval writes a `RegExp` as a regular expression literal. In affected versions, the `\u003c` character in a `RegExp` source is written without escaping. A source built from untrusted input can then end the HTML `\u003cscript\u003e` element that the serialized output is placed in, and run script in the page.\n\n### Details\n\nseroval escapes `\u003c` in strings, so string values cannot end a `\u003cscript\u003e` element. `RegExp` sources did not get the same escaping:\n\n- Versions before 1.0.0 wrote the source as is.\n- Version 1.5.5 stopped escaping `\u003c` in `RegExp` sources, so that named groups and lookbehinds keep working. This removed the escaping for every `\u003c` in a source.\n\nThese functions are affected:\n\n- `serialize`, `serializeAsync`\n- `crossSerialize`, `crossSerializeAsync`, `crossSerializeStream`\n- the `Serializer` class\n- `compileJSON`\n\n`toJSON`, `fromJSON`, `toCrossJSON` and `fromCrossJSON` are not affected, because they never produce JavaScript.\n\n### Impact\n\nAn application is affected when all of these are true:\n\n1. It builds a `RegExp` from untrusted input that is used as regular expression syntax. Input passed through an escaping helper (such as an `escapeRegExp` function) is not enough to exploit this.\n2. It serializes that `RegExp` with one of the functions above.\n3. It places the output inside an HTML `\u003cscript\u003e` element, as server rendering usually does.\n\nIn that case an attacker can run script in the page of any user who receives that output.\n\n### Patches\n\nFixed in 1.6.10. A `RegExp` whose source contains `\u003c` is now written with the `RegExp` constructor and an escaped string source. Named groups and lookbehinds keep working.\n\n### Workarounds\n\nIf you cannot upgrade:\n\n- Do not serialize a `RegExp` built from untrusted pattern syntax. Send its source and flags as strings, and build the `RegExp` on the client.\n- Or reject patterns that contain `\u003c` before they reach the serializer.","aliases":["CVE-2026-116582"],"modified":"2026-10-28T21:30:04.992414732Z","published":"2026-10-28T21:17:31Z","database_specific":{"cwe_ids":["CWE-116","CWE-79"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-10-28T21:17:31Z","nvd_published_at":"2026-10-26T21:18:16Z"},"references":[{"type":"WEB","url":"https://github.com/lxsmnsyc/seroval/security/advisories/GHSA-9wx9-5pv9-3349"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-116582"},{"type":"WEB","url":"https://github.com/lxsmnsyc/seroval/commit/f94ee0b63936dae954ff50d5b5e8ea7cb9b284e6"},{"type":"PACKAGE","url":"https://github.com/lxsmnsyc/seroval"},{"type":"WEB","url":"https://github.com/lxsmnsyc/seroval/releases/tag/seroval@1.6.10"}],"affected":[{"package":{"name":"seroval","ecosystem":"npm","purl":"pkg:npm/seroval"},"ranges":[{"type":"SEMVER","events":[{"introduced":"1.5.5"},{"fixed":"1.6.10"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-9wx9-5pv9-3349/GHSA-9wx9-5pv9-3349.json"}},{"package":{"name":"seroval","ecosystem":"npm","purl":"pkg:npm/seroval"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.0.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-9wx9-5pv9-3349/GHSA-9wx9-5pv9-3349.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N"}]}