CVE-2026-12866
Description
A flaw was found in expr-eval. A remote attacker can exploit this vulnerability by supplying crafted expressions to the toJSFunction() API. These expressions are then compiled into native code using new Function(), allowing the attacker to execute arbitrary JavaScript code. This can lead to arbitrary code execution within the application's context, potentially compromising the system.
Statement
RHEL AI 3.4 bootc images ship expr-eval@2.0.2 as a dependency of @langchain/community. The only identified consumer is the LangChain Calculator tool, which calls Parser.evaluate() and does not invoke toJSFunction(). CVE-2026-12866 affects only the toJSFunction() API. No other npm package in the image depends on expr-eval. For this reason the issue is rated Low for RHEL AI.
Mitigation
LangChainJS already replaced expr-eval with math-expression-evaluator in a later @langchain/community release (fix for CVE-2025-12735). Bootc owners should bump @langchain/community to a version that no longer bundles expr-eval, which removes the dead dependency entirely.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.2 | N/A | 9.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | High |
| Integrity Impact | Low | N/A | High |
| Availability Impact | None | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
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