CVE-2026-97711: Serialize JavaScript Cross-Site Scripting Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gfhx-hw2g-v5hg",
  "modified" : "2026-09-30T15:40:06Z",
  "published" : "2026-09-30T15:40:05Z",
  "aliases" : [ "CVE-2026-97711" ],
  "summary" : "Serialize JavaScript: Cross-site scripting (XSS) via unescaped </script> in serialized function bodies",
  "details" : "### Impact\n\n`serialize-javascript` escapes its output so it is safe to embed inside a\n`<script>` element. In 7.1.1 that guarantee does not hold for **function\nvalues**: a crafted function body can carry a literal, unescaped `</script>`\ninto the output, terminating the script element early so the remainder is\nparsed as HTML.\n\n`SCRIPT_CLOSE_REGEXP` used `<\\/script[^>]*>` as its first alternative. The\ncharacter class excludes only `>`, so a single match could run from one\n`</script` all the way to the next `>` anywhere in the source — swallowing a\nsecond, complete `</script>` along the way. Only one replacement is emitted\nper match, and the plain-code branch neutralizes just the leading `<`\n(`'< ' + match.slice(1)`), so the swallowed tag was re-emitted verbatim.\n\nReaching that shape requires `</script` in code position, which is legal\nJavaScript: `x</script=+/` parses as `x < /script=+/`, a comparison against a\nregex literal.\n\n```js\nconst serialize = require('serialize-javascript');\nconst src = \"function f(x){ return x</script=+/ + '</script><img src=x onerror=alert(1)>' }\";\nconst out = serialize({ h: new Function('return ' + src)() });\n// {\"h\":function f(x){ return x< /script=+/ + '</script><img src=x onerror=alert(1)>' }}\n```\n\nEmbedded as the README documents (`<script>window.S = <%= serialize(state) %></script>`)\nand parsed by Chromium, the script element ends at the injected tag and the\n`<img>` becomes a live DOM node with its `onerror` handler executing in the\npage origin.\n\nOnly the function path is affected. The same payload passed as **data** is\nescaped correctly, and `options.isJSON` / non-function values are unaffected.\n\n### Patches\n\nFixed in **7.1.2**. The wildcard now excludes `<` as well as `>`\n(`[^<>]*`), so a match can never reach past a second `<`. Every `</script`\nin the source therefore either begins its own match or is followed by a\ncharacter the HTML tokenizer does not accept as ending a tag name — it ends\nthe tag name only on TAB, LF, FF, CR, SPACE, `/` or `>`, and emits anything\nelse as text.\n\n### Workarounds\n\nUpgrade to **7.1.2**. If you cannot upgrade, 7.1.0 and earlier are\nunaffected, or avoid serializing functions whose source text is\nattacker-influenced.\n\n### Regression note\n\nThis is a regression specific to 7.1.1, not a long-standing issue. 7.1.0 and\nearlier applied the same wildcard but escaped the **entire** match, so no tag\nsurvived. Downstream scanners defaulting to a `>= 7.1.0` range would be\noverly broad.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "serialize-javascript"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.1.1"
      }, {
        "fixed" : "7.1.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/yahoo/serialize-javascript/security/advisories/GHSA-gfhx-hw2g-v5hg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-97711"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yahoo/serialize-javascript/commit/2bdbaaff9cb8a4639135eb24cfcd383d3fefb534"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/yahoo/serialize-javascript"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yahoo/serialize-javascript/releases/tag/v7.1.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79", "CWE-80" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-30T15:40:05Z",
    "nvd_published_at" : "2026-09-29T16:17:19Z"
  }
}