CVE Watch21 jul 2026

CVE-2026-35209

defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user

CVSS

7.5

Alto

EPSS

0.4%

p34

KEV

—

Exploit Today

0-100

Publicado: 6 abr 2026 · Última mod.: 21 jul 2026 · CWE-1321

EPSS · 30d

0.4%EPSS · 30 días0.4%

2026-08-252026-09-22

Descripción técnica

defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to `defu()` are vulnerable to prototype pollution. A crafted payload containing a `__proto__` key can override intended default values in the merged resul. The internal `_defu` function used `Object.assign({}, defaults)` to copy the defaults object. `Object.assign` invokes the `__proto__` setter, which replaces the resulting object's `[[Prototype]]` with attacker-controlled values. Properties inherited from the polluted prototype then bypass the existing `__proto__` key guard in the `for...in` loop and land in the final result. Version 6.1.5 replaces `Object.assign({}, defaults)` with object spread (`{ ...defaults }`), which uses `[[DefineOwnProperty]]` and does not invoke the `__proto__` setter.

Referencias oficiales

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