Vulnerability-Lookup

CVE-2026-115897 (GCVE-0-2026-115897)

Vulnerability from cvelistv5 – Published: 2026-10-23 21:37 – Updated: 2026-10-26 17:41

Title

Serialize JavaScript: Cross-site scripting (XSS) via unescaped </script at the end of a serialized function body

Summary

Serialize JavaScript serializes JavaScript values to a superset of JSON that includes regular expressions and functions. Prior to 7.1.3, the function-source escaping logic does not neutralize a bare closing-script prefix when attacker-influenced function source text ends exactly at that prefix. Because each function body is escaped independently, a delimiter supplied by surrounding serialized output can terminate an HTML script element, and a later serialized value supplies injected markup that becomes a live element in the page. Exploitation requires control of a serialized function's source text, such as through a spoofed toString(). This issue is fixed in version 7.1.3.

Severity

2.1 (Low)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-26 15:39 UTC

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 8083 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/yahoo/serialize-javascript/sec…	x_refsource_CONFIRM
https://github.com/yahoo/serialize-javascript/pull/235	x_refsource_MISC
https://github.com/yahoo/serialize-javascript/com…	x_refsource_MISC
https://github.com/yahoo/serialize-javascript/rel…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
yahoo	serialize-javascript	Affected: < 7.1.3	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-115897

Vulnerability from fkie_nvd - Published: 2026-10-23 22:16 - Updated: 2026-10-26 18:39

Severity

2.1 (Low) - CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/yahoo/serialize-javascript/commit/2864b3c6260a3bfd52d2db3e70d1a079de108a61
	security-advisories@github.com	https://github.com/yahoo/serialize-javascript/pull/235
	security-advisories@github.com	https://github.com/yahoo/serialize-javascript/releases/tag/v7.1.3
	security-advisories@github.com	https://github.com/yahoo/serialize-javascript/security/advisories/GHSA-m5mm-p8h7-m29v

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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      "affectedData": [
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          "product": "serialize-javascript",
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    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/yahoo/serialize-javascript/security/advisories/GHSA-m5mm-p8h7-m29v"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-M5MM-P8H7-M29V

Vulnerability from github – Published: 2026-10-23 22:09 – Updated: 2026-10-23 22:09

Summary

Serialize JavaScript: Cross-site scripting (XSS) via unescaped </script at the end of a serialized function body

Details

Impact

serialize-javascript escapes its output so it is safe to embed inside a <script> element. Before 7.1.3 that guarantee did not hold for a function value whose source ends in a bare </script.

Each function body is escaped on its own, and a bare </script was only neutralized when followed — within the same body — by a character the HTML tokenizer treats as ending the tag name (TAB, LF, FF, CR, SPACE, / or >). A body ending exactly at </script has no following character, so it was emitted unescaped. The delimiter is then supplied by the surrounding output (for example the newline the space option emits after the value), and a later serialized value can supply the closing > followed by markup:

const serialize = require('serialize-javascript');
function f() {} f.toString = () => 'function f(){ return 1 }//</script';
function g() {} g.toString = () => 'function g(x){ return x } > <img src=x onerror=alert(1)>';
serialize({ a: { f }, g }, { space: 2 });
// {
//   "a": {
//     "f": function f(){ return 1 }//</script
//   },
//   "g": function g(x){ return x } > <img src=x onerror=alert(1)>
// }

Embedded in a <script> element, the script ends at the injected tag and the <img> becomes a live element in the page.

Exploitation requires an attacker to control the source text of a serialized function, in practice through a spoofed toString(). Real functions always end in }, so ordinary function values are not affected, and non-function values (including strings containing </script) are escaped correctly.

Patches

Fixed in 7.1.3 (#235). The bare </script form is now also matched at the end of the function body, so it is escaped regardless of what follows it in the output.

Workarounds

Upgrade to 7.1.3. If you cannot upgrade, do not serialize function values whose source text (or toString()) can be influenced by an attacker.

Credits

Reported by ha_kr25 via the Yahoo bug bounty program.

Severity

2.1 (Low)


                  
                    CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "serialize-javascript"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.1.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-115897"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-23T22:09:52Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Impact\n\n`serialize-javascript` escapes its output so it is safe to embed inside a\n`\u003cscript\u003e` element. Before 7.1.3 that guarantee did not hold for a **function\nvalue whose source ends in a bare `\u003c/script`**.\n\nEach function body is escaped on its own, and a bare `\u003c/script` was only\nneutralized when followed \u2014 within the same body \u2014 by a character the HTML\ntokenizer treats as ending the tag name (TAB, LF, FF, CR, SPACE, `/` or `\u003e`).\nA body ending exactly at `\u003c/script` has no following character, so it was\nemitted unescaped. The delimiter is then supplied by the surrounding output\n(for example the newline the `space` option emits after the value), and a\nlater serialized value can supply the closing `\u003e` followed by markup:\n\n```js\nconst serialize = require(\u0027serialize-javascript\u0027);\nfunction f() {} f.toString = () =\u003e \u0027function f(){ return 1 }//\u003c/script\u0027;\nfunction g() {} g.toString = () =\u003e \u0027function g(x){ return x } \u003e \u003cimg src=x onerror=alert(1)\u003e\u0027;\nserialize({ a: { f }, g }, { space: 2 });\n// {\n//   \"a\": {\n//     \"f\": function f(){ return 1 }//\u003c/script\n//   },\n//   \"g\": function g(x){ return x } \u003e \u003cimg src=x onerror=alert(1)\u003e\n// }\n```\n\nEmbedded in a `\u003cscript\u003e` element, the script ends at the injected tag and the\n`\u003cimg\u003e` becomes a live element in the page.\n\nExploitation requires an attacker to control the **source text** of a\nserialized function, in practice through a spoofed `toString()`. Real\nfunctions always end in `}`, so ordinary function values are not affected,\nand non-function values (including strings containing `\u003c/script`) are\nescaped correctly.\n\n### Patches\n\nFixed in **7.1.3** (#235). The bare `\u003c/script` form is now also matched at\nthe end of the function body, so it is escaped regardless of what follows it\nin the output.\n\n### Workarounds\n\nUpgrade to **7.1.3**. If you cannot upgrade, do not serialize function values\nwhose source text (or `toString()`) can be influenced by an attacker.\n\n### Credits\n\nReported by **ha_kr25** via the Yahoo bug bounty program.",
  "id": "GHSA-m5mm-p8h7-m29v",
  "modified": "2026-10-23T22:09:52Z",
  "published": "2026-10-23T22:09:52Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/yahoo/serialize-javascript/security/advisories/GHSA-m5mm-p8h7-m29v"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yahoo/serialize-javascript/pull/235"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yahoo/serialize-javascript/commit/2864b3c6260a3bfd52d2db3e70d1a079de108a61"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/yahoo/serialize-javascript"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yahoo/serialize-javascript/releases/tag/v7.1.3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Serialize JavaScript: Cross-site scripting (XSS) via unescaped \u003c/script at the end of a serialized function body"
}

MSRC_CVE-2026-115897

Vulnerability from csaf_microsoft - Published: 2026-10-29 01:09 - Updated: 2026-10-29 01:09

Summary

Serialize JavaScript: Cross-site scripting (XSS) via unescaped </script at the end of a serialized function body

Scope

1 vulnerability in this advisory, including CVE-2026-115897.

CVE-2026-115897

Known affected: 1 product

Open the full advisory

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2026-115897 (GCVE-0-2026-115897)

FKIE_CVE-2026-115897

GHSA-M5MM-P8H7-M29V

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MSRC_CVE-2026-115897

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