CVE-2026-12866: expr-eval vulnerable to Code Execution

June 23, 2026 (updated September 22, 2026)

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.

References

github.com/advisories/GHSA-q9v2-7m5w-4693
github.com/silentmatt/expr-eval/blob/master/src/expression.js
github.com/silentmatt/expr-eval/issues/292
nvd.nist.gov/vuln/detail/CVE-2026-12866
security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-17662018
security.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690

Code Behaviors & Features

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