Elo Ruby backend has Remote Code Execution via unescaped #{...} interpolation in emitted string literals and subtype-constraint labels

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary Elo's Ruby backend emits attacker-controlled text into Ruby double-quoted strings without escaping the `#` character. Because `#` begins Ruby's interpolation sequences — `#{expr}`, `#@ivar`, `#@@cvar`, `#$gvar` — and any expression wrapped in `#{...}` may use backticks for shell execution, an Elo program that contains a crafted string literal or a labelled subtype constraint compiles to Ruby that evaluates attacker-chosen Ruby, and through backticks runs attacker-chosen shell commands, at runtime. The same Elo source compiled to JavaScript, Python, or SQL is benign, so the bug also breaks the cross-target portability guarantee the rest of the compiler honours.

Vulnerable sinks Two sinks exist in `src/compilers/ruby.ts` at commit `749af7b`: 1. String-literal emitter — lines 180–184. The emitter escapes backslash, double quote, and control characters, but not `#`. Any `#{...}` sequence in an Elo string literal flows straight into the emitted Ruby source. 2.…

Published by the source

3 Nov 2026, 17:51 UTC

Last modified by the source

3 Nov 2026, 18:02 UTC

Source last checked

4 Nov 2026, 06:10 UTC

1. Revision 2 · amended · 4 Nov 2026

   Amended from osv record GHSA-7w38-ggh5-v542

2. Revision 1 · created · 3 Nov 2026

   Published from ghsa record GHSA-7w38-ggh5-v542

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# Patch Next advisory brief: CVE-2026-44266

Advisory: Elo Ruby backend has Remote Code Execution via unescaped `#{...}` interpolation in emitted string literals and subtype-constraint labels
IDs: CVE-2026-44266, GHSA-7w38-ggh5-v542
Record: https://patchnext.com/advisories/cve-2026-44266 (revision 2, source checked 4 Nov 2026, 06:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @enspirit/elo 1.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @enspirit/elo: affected < 1.0.1; fixed in 1.0.1

## Suggested inspection (read-only)
- `npm ls @enspirit/elo --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @enspirit/elo.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-7w38-ggh5-v542 (GitHub-reviewed advisory GHSA-7w38-ggh5-v542 lists affected ranges: npm @enspirit/elo >=0 <=1.0.0)
- Verified: https://osv.dev/vulnerability/GHSA-7w38-ggh5-v542 (OSV record GHSA-7w38-ggh5-v542 lists affected ranges: npm @enspirit/elo >=0 <1.0.1 (fixed))

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