silentmatt expr-eval Expressions toJSFunction code injection

Summaryinfo

A vulnerability has been found in silentmatt expr-eval and classified as critical. This impacts the function toJSFunction of the component Expressions Handler. This manipulation causes code injection. This vulnerability is registered as CVE-2026-12866. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability has been found in silentmatt expr-eval (the affected version unknown) and classified as critical. Affected by this vulnerability is the function toJSFunction of the component Expressions Handler. The manipulation with an unknown input leads to a code injection vulnerability. The CWE definition for the vulnerability is CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at security.snyk.io. This vulnerability is known as CVE-2026-12866 since 06/22/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/23/2026). MITRE ATT&CK project uses the attack technique T1059 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-38415). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• silentmatt

Name

• expr-eval

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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