Plattform
nodejs
Komponente
defu
Behoben in
6.1.6
6.1.5
CVE-2026-35209 describes a prototype pollution vulnerability affecting the defu package. The vulnerability arises when applications pass unsanitized user input as the first argument to the defu() function. A crafted payload containing a proto key can override intended default values in the merged result, leading to unexpected behavior or security implications. This issue is resolved in version 6.1.5.
Prototype pollution occurs when an attacker can modify the prototype of JavaScript objects, effectively altering the behavior of all objects inheriting from that prototype. In the context of defu, an attacker can inject a proto key into user-supplied data (like JSON request bodies or configuration files) and pass it to the defu() function. This allows them to override intended default values, potentially granting unauthorized access or modifying application logic. For example, an attacker could set isAdmin: true to bypass access controls. The blast radius extends to any part of the application relying on the defu function and its default values, making it a significant security concern.
This vulnerability was publicly disclosed on 2026-04-04. While no active exploitation campaigns have been publicly reported, the ease of exploitation and the potential impact make it a high-priority concern. The vulnerability is not currently listed on CISA KEV. Public proof-of-concept code is likely to emerge, increasing the risk of widespread exploitation.
Applications built with Node.js that utilize the defu package for managing configuration or default values are at risk. This includes web applications, APIs, and backend services. Specifically, applications that parse user-supplied JSON data or load configuration files from untrusted sources are particularly vulnerable.
• nodejs / server:
npm audit defu• nodejs / supply-chain:
find . -name 'package.json' -print0 | xargs -0 grep '"defu": ["^6.1.5"']• generic web: Inspect application logs for unusual object properties or unexpected behavior after processing user input. Look for instances where default values are being unexpectedly overridden.
disclosure
Exploit-Status
EPSS
0.04% (12% Perzentil)
CISA SSVC
CVSS-Vektor
The primary mitigation for CVE-2026-35209 is to upgrade to defu version 6.1.5 or later, which includes a fix for the vulnerability. If upgrading is not immediately feasible, implement strict input sanitization on any user-supplied data passed to defu(). This involves validating and filtering input to prevent the injection of malicious proto payloads. Consider using a dedicated input validation library to ensure comprehensive protection. Additionally, review application code that utilizes defu to identify potential areas where prototype pollution could be exploited. After upgrading, confirm the fix by attempting to trigger the prototype pollution vulnerability with a crafted payload and verifying that the default values are not overridden.
Actualiza la librería 'defu' a la versión 6.1.5 o superior para mitigar la vulnerabilidad de contaminación de prototipos. Esto se soluciona reemplazando `Object.assign({}, defaults)` con object spread (`{ ...defaults }`), que evita la invocación del setter `__proto__`.Schwachstellenanalysen und kritische Warnungen direkt in deinen Posteingang.
CVE-2026-35209 is a HIGH severity prototype pollution vulnerability in the defu Node.js package, allowing attackers to override default values through crafted payloads.
You are affected if you are using defu versions prior to 6.1.5 and pass unsanitized user input to the defu() function.
Upgrade to defu version 6.1.5 or later. If upgrading is not possible, implement strict input sanitization on any user-supplied data passed to defu().
No active exploitation campaigns have been publicly reported, but the vulnerability's ease of exploitation warrants immediate attention.
Refer to the defu project's repository and associated release notes for the official advisory and details on the fix.
Lade deine Abhängigkeitsdatei hoch und erfahre sofort, ob dich diese und andere CVEs treffen.