Lodash <4.18.0 _.template key-names RCE
CVE-2026-4800 Published on March 31, 2026
lodash vulnerable to Code Injection via `_.template` imports key names
Impact:
The fix for CVE-2021-23337 (https://github.com/advisories/GHSA-35jh-r3h4-6jhm) added validation for the variable option in _.template but did not apply the same validation to options.imports key names. Both paths flow into the same Function() constructor sink.
When an application passes untrusted input as options.imports key names, an attacker can inject default-parameter expressions that execute arbitrary code at template compilation time.
Additionally, _.template uses assignInWith to merge imports, which enumerates inherited properties via for..in. If Object.prototype has been polluted by any other vector, the polluted keys are copied into the imports object and passed to Function().
Patches:
Users should upgrade to version 4.18.0.
Workarounds:
Do not pass untrusted input as key names in options.imports. Only use developer-controlled, static key names.
Weakness Type
What is a Code Injection Vulnerability?
The software 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.
CVE-2026-4800 has been classified to as a Code Injection vulnerability or weakness.
Products Associated with CVE-2026-4800
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Affected Versions
lodash:- Version 4.0.0 and below 4.18.0 is affected.
- Version 4.18.0 is unaffected.
- Version 4.0.0 and below 4.18.0 is affected.
- Version 4.18.0 is unaffected.
- Version 4.0.0 and below 4.18.0 is affected.
- Version 4.18.0 is unaffected.
- Version 4.0.0 and below 4.18.0 is affected.
- Version 4.18.0 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.