External risk intelligence

Elo Expression Language Code Injection

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-44267

Elo is a library for expression parsing. While it can be used in internet-facing contexts like a playground, web-based tools, or server-side applications processing user input, it is fundamentally a development library and language component. Its exposure depends entirely on whether a developer integrates it into a public-facing service or an internal utility, making broad internet reachability possible but not inherent.

Cross-site Scripting

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory highlights a critical security vulnerability in the Elo expression language, which is used in no-code tools. The flaw allows attackers to execute arbitrary code, potentially leading to unauthorized access and compromise of systems that process Elo strings. The primary concern is to confirm if and where this technology is used within our environment to assess potential exposure.

Allows code execution via input strings.
Matters if Elo processes external input.
Confirm relevance and scope within our systems.

Attack Path

How an attacker could exploit the issue

An attacker can exploit this vulnerability by providing specially crafted Elo strings to vulnerable parsing functions or tools. This allows them to inject malicious code that will be executed by the underlying JavaScript runtime, potentially leading to unauthorized code execution.

No special access required.
Malicious Elo strings parsed.
Arbitrary code execution risk.

Live Threat

Current exploitation, exposure, and threat context

Plain Elo strings processed by specific functions or the online playground could allow attackers to execute arbitrary JavaScript or Node.js code. This occurs because the language does not adequately validate certain string inputs, enabling them to reach underlying JavaScript execution capabilities. This could affect the integrity and confidentiality of systems where Elo is used to process untrusted input, particularly in web-based tools or server-side applications.

System code and sensitive information.
Via crafted Elo strings in supported applications.
Arbitrary code execution and session compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Elo expression language vulnerability impacts users of no-code tools, potentially exposing applications to arbitrary code execution. Teams responsible for no-code platforms, CI/CD pipelines, or DevOps tools integrating Elo should prioritize identifying all deployments, assessing their exposure and criticality, and coordinating with vendors or development teams for remediation.

Platform and application owners should lead remediation.
Verify all Elo deployments and their reachability.
Plan for updates based on identified risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Elo and where is it used?

Elo is a purely functional expression language designed for no-code tools. Developers integrate it as a library to parse and evaluate logic strings within applications. It is frequently used in web-based playgrounds, CI/CD pipelines, and various DevOps or automation tools to enable dynamic functional programming capabilities.

What is the vulnerability in CVE-2026-44267?

This vulnerability involves Improper Neutralization of Input During Code Generation (CWE-94). The language parser fails to block specific meta-properties, allowing an attacker to manipulate Elo strings to access the underlying JavaScript Function constructor. This effectively breaks the sandbox, enabling the execution of arbitrary, unauthorized code within the host's runtime environment.

How does an attacker trigger this vulnerability?

An attacker triggers this by submitting a specially crafted plain Elo string to vulnerable functions like defaultFormats.elo.parse() or command-line utilities. Crucially, this bug specifically concerns plain-string inputs; it does not apply to programmatic interactions where developers utilize pre-validated AST-object structures instead of raw, unparsed strings.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal identifies this as a potential risk depending on your implementation. While Elo is a development component, the risk is highest if you have integrated it into internet-facing services, such as a public web tool or a playground that accepts user-supplied input. Internal utilities using Elo are generally at lower risk but still vulnerable if they process untrusted data.

How do I address CVE-2026-44267 in my environment?

The primary response is to update your Elo dependency to version 1.0.1, which includes the necessary security fixes. Start by auditing your codebase to locate where the library is utilized. Prioritize applications that process external, untrusted input strings, as these represent the most significant attack surface for potential code execution.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.