{"id":"CVE-2026-116582","aliases":["GHSA-9wx9-5pv9-3349"],"title":"Seroval: Script injection through RegExp sources in serialized output","summary":"Seroval: Script injection through RegExp sources in serialized output","severity":"medium","cvss":4.7,"cwe":["CWE-79","CWE-116"],"vendor":"seroval","product":"seroval","ecosystem":"npm","affected":["seroval >= 1.5.5, < 1.6.10","seroval < 1.0.0"],"patched":["seroval 1.6.10","seroval 1.0.0"],"published":"2026-10-28","updated":"2026-10-28","sourceUpdated":"2026-10-28T21:17:32Z","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-9wx9-5pv9-3349","references":[{"url":"https://github.com/lxsmnsyc/seroval/security/advisories/GHSA-9wx9-5pv9-3349"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-116582"},{"url":"https://github.com/lxsmnsyc/seroval/commit/f94ee0b63936dae954ff50d5b5e8ea7cb9b284e6"},{"url":"https://github.com/lxsmnsyc/seroval/releases/tag/seroval@1.6.10"},{"url":"https://github.com/advisories/GHSA-9wx9-5pv9-3349"}],"tags":["ghsa","npm","cve.org"],"epss":0.00188,"epssPercentile":0.08357,"ingestedAt":"2026-10-27T16:11:59.112Z","slug":"CVE-2026-116582","body":"## Overview\n\n### Summary\n\nseroval writes a `RegExp` as a regular expression literal. In affected versions, the `<` character in a `RegExp` source is written without escaping. A source built from untrusted input can then end the HTML `<script>` element that the serialized output is placed in, and run script in the page.\n\n### Details\n\nseroval escapes `<` in strings, so string values cannot end a `<script>` 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 `<` in `RegExp` sources, so that named groups and lookbehinds keep working. This removed the escaping for every `<` 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 `<script>` 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 `<` 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 `<` before they reach the serializer.\n\n## Affected packages\n\n- `seroval >= 1.5.5, < 1.6.10`\n- `seroval < 1.0.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `seroval 1.6.10`\n- `seroval 1.0.0`","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":25.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}