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CVE-2026-12866

9.8 · CRITICAL

All versions of the package expr-eval are vulnerable to Code Execution via the toJSFunction() API.

Published Jun 23, 2026CWE-94EPSS 0.87%

Overview

CVE-2026-12866 is a critical-severity vulnerability. It was published on June 23, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/silentmatt/expr-eval/blob/master/src/expression.js%23L55GitHubgithub.com/silentmatt/expr-eval/issues/292Refsecurity.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-17662018Refsecurity.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690Refsecurity.snyk.io/vuln/SNYK-JS-EXPREVAL-15054690

How CyberStrike helps

Frequently asked questions

What is CVE-2026-12866?

CVE-2026-12866 is a critical-severity vulnerability. It was published on June 23, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-12866?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-12866?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-12866?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-12866 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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