Summary
deepmerge mergeObject() allows prototype poisoning of returned objects
deepmerge through 4.3.1 contains a prototype poisoning vulnerability in the mergeObject() function that fails to properly validate keys being written to target objects. Attackers can supply malicious source objects in merge operations to inject attacker-controlled properties into the returned object's prototype, causing applications to inherit unintended values when accessing properties without own-property checks.
Impact
CVE-2026-93753 has a CVSS score of 5.3 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-93753? CVE-2026-93753 is a low-severity security vulnerability in deepmerge (npm), affecting versions >= 4.2.0, <= 4.3.1. No fixed version is listed yet.
- How severe is CVE-2026-93753? CVE-2026-93753 has a CVSS score of 5.3 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of deepmerge are affected by CVE-2026-93753? deepmerge (npm) versions >= 4.2.0, <= 4.3.1 is affected.
- Is there a fix for CVE-2026-93753? No fixed version is listed for CVE-2026-93753 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-93753 exploitable, and should I be worried? Whether CVE-2026-93753 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-93753 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.