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CVE-2026-12866

Status: DeferredCritical (9.2)—

All versions of the package expr-eval are vulnerable to Code Execution via the toJSFunction() API. An attacker can execute arbitrary JavaScript by supplying crafted expressions that are compiled into native code using new Function(). Because user-controlled expressions are transformed directly into executable JavaScript, attackers can escape the intended expression sandbox and run arbitrary code within the application's context.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

Vulnerabilidad de código en librería JavaScript accesible remotamente (T1190, AV:N). Ejecuta JavaScript arbitrario via toJSFunction() compilando expresiones maliciosas con new Function() (T1059.007, CWE-94 remota code execution). Potencial acceso a datos en contexto de aplicación (T1005).

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Vulnerability ScanningRestrict Web-Based ContentPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkFilter Network Traffic

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Expr-eval — Expr-evalAI

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-12866",
  "cveTags": [],
  "metrics": {
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          "options": [
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          "version": "2.0.3",
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  "published": "2026-06-23T05:17:03.380",
  "references": [
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      "url": "https://github.com/silentmatt/expr-eval/blob/master/src/expression.js%23L55",
      "source": "report@snyk.io"
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    {
      "url": "https://github.com/silentmatt/expr-eval/issues/292",
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      "url": "https://security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-17662018",
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      "url": "https://security.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690",
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      "lang": "en",
      "value": "All versions of the package expr-eval are vulnerable to Code Execution via the toJSFunction() API. An attacker can execute arbitrary JavaScript by supplying crafted expressions that are compiled into native code using new Function(). Because user-controlled expressions are transformed directly into executable JavaScript, attackers can escape the intended expression sandbox and run arbitrary code within the application's context."
    }
  ],
  "lastModified": "2026-07-07T19:16:51.120",
  "sourceIdentifier": "report@snyk.io"
}