External risk intelligence

Elo Ruby Backend Code Injection Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-44266

The vulnerability affects a functional expression language library used in no-code tools. While the playground and command-line tools are entry points, the library itself is typically integrated into larger applications. Reachability depends on whether an application exposes the language parsing or compilation functionality to user-supplied input, making public internet exposure possible but not inherently guaranteed by the library's design.

Code Injection

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 details a critical vulnerability in the Elo expression language, specifically within its Ruby backend. The flaw allows for the execution of arbitrary Ruby code and shell commands when processing specially crafted input, potentially impacting systems that use Elo for no-code tools and their Ruby compilation.

Code execution flaw in expression language.
Matters for code integrity and system control.
Confirm relevance and assess potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this by tricking the Ruby backend of the Elo expression language into evaluating specially crafted strings. This could happen through the /try playground, command-line interface, or when using the parse function directly if the output is then compiled to Ruby. Successful exploitation allows the attacker to run arbitrary Ruby code and shell commands on the system.

Unauthenticated access to vulnerable entry points.
Evaluating attacker-controlled strings as Ruby code.
Arbitrary code and shell command execution.

Live Threat

Current exploitation, exposure, and threat context

When Elo's Ruby backend embeds attacker-controlled text in Ruby double-quoted strings without proper escaping, it can lead to the execution of arbitrary Ruby code and shell commands. This can occur through the /try playground with the Ruby target, the `bin/eloc -t ruby -x` command, or when `defaultFormats.elo.parse()` is followed by Ruby emission.

Arbitrary Ruby code execution.
Via embedded, unescaped attacker input.
System compromise or unauthorized actions.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability within the Elo Ruby backend may require coordination between application owners who integrate Elo, platform teams managing no-code tool infrastructure, and potentially vendor management if Elo is a third-party component. The first practical step is to identify all instances of Elo, confirm their exposure and criticality, and then engage the accountable owner to plan remediation by the updated version.

Application owners and platform teams.
Verify Elo's Ruby backend usage and reachability.
Plan upgrade or implement compensating controls.

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?

Elo is a purely functional expression language designed for no-code development platforms. It allows users to define logic or constraints that the system then translates into various programming languages, including Ruby, JavaScript, Python, or SQL, to perform specific tasks within those applications.

How does CVE-2026-44266 lead to code execution?

This vulnerability involves Improper Neutralization of Input during Code Generation (CWE-94, CWE-116). Because the Ruby backend fails to properly escape special characters, an attacker can embed malicious Ruby interpolation sequences into a string. When the compiled Ruby code runs, it treats this injected text as executable commands, potentially allowing unauthorized shell command execution.

Does this vulnerability affect JavaScript or Python output?

No. The flaw is specific to the Ruby backend's string-literal emitter in Elo. When the system is configured to emit code for JavaScript, Python, or SQL, this specific injection path is not triggered. The risk is isolated to workflows where Elo compiles expressions into Ruby code.

Is my system at risk if I use Elo?

Halo Surface Signal indicates that while the Ruby backend is vulnerable, your actual risk depends on whether your application exposes Elo’s parsing or compilation features to untrusted user input. If your system allows users to provide input that the Elo library then processes and emits as Ruby, it may be exposed to the internet or other users.

What should I do to address this issue?

The first step is to inventory where Elo is deployed in your environment and determine if the Ruby emission feature is active. Once identified, coordinate with your application teams to upgrade to version 1.0.1 or later, which contains the necessary fixes for the string-escaping logic.

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.