CVE-2026-12866 Details
Description
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.
A code execution vulnerability has been identified in all versions of the expr-eval package. The issue arises in the toJSFunction() API, where user-supplied expressions are compiled into executable JavaScript using new Function(). This allows attackers to execute arbitrary code within the application's context by escaping the intended expression sandbox. The vulnerability is particularly concerning in Node.js environments, where access to global variables like process can be exploited.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jun 23, 2026CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://security.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690 | CISA-ADP | AdvisoryExploit |
| https://github.com/silentmatt/expr-eval/blob/master/src/expression.js%23L55 | [email protected] | Broken LinkSource CodeVendor |
| https://github.com/silentmatt/expr-eval/issues/292 | [email protected] | ExploitIssue TrackingTechnical DescriptionVendor |
| https://security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-17662018 | [email protected] | |
| https://security.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690 | [email protected] | AdvisoryExploit |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-94 | Improper Control of Generation of Code ('Code Injection') | CISA-ADP |
| CWE-94 | Improper Control of Generation of Code ('Code Injection') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| expr-eval | < 1.0.0 (semver) |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 7, 2026 | CVE Modified | [email protected] |
| Jun 23, 2026 | CVE Modified | CISA-ADP |
| Jun 23, 2026 | New CVE Received | [email protected] |