Weakness (CWE)
CWE-1321: Improperly Controlled Modification of Object Prototype Attributes
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
How to prevent it (5 mitigations)
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Implementation
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
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Architecture and Design
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
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Implementation
When handling untrusted objects, validating using a schema can be used.
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Implementation
By using an object without prototypes (via Object.create(null) ), adding object prototype attributes by accessing the prototype via the special attributes becomes impossible, mitigating this weakness.
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Implementation
Map can be used instead of objects in most cases. If Map methods are used instead of object attributes, it is not possible to access the object prototype or modify it.
Source: MITRE CWE-1321
712 results · Feed
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High 8.2
Prototype Pollution in parse-nested-form-data via `__proto__` in FormData field names
parse-nested-form-data is a tiny node module for parsing FormData by name into objects and arrays. Prior to version 1.0.1, parseFormData() walks bracket and dot-notation FormData field names into nested objects without filtering reserved property keys. A sing…
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High 8.2
Prototype pollution in form-data-objectizer via bracket-notation form keys
form-data-objectizer converts FormData to object. Prior to 1.0.1, form-data-objectizer walks bracket-notation form keys (e.g. name[sub]) into nested objects without filtering __proto__, constructor, or prototype. A single HTTP form field whose name starts wit…
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High 8.2
deepobj: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
deepobj provides get, set, delete deep objects in javascript. Prior to 1.0.3, prototype pollution is possible when property paths contain __proto__/constructor/prototype. The property path must not be exposed as user input. This vulnerability is fixed in 1.0.…
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High 8.2
RVF: Prototype pollution in @rvf/set-get reachable via @rvf/core preprocessFormData (HTTP form data)
RVF (formerly Remix Validated Form) provides easy form validation and state management for React. From 6.0.0 to before 6.0.4 and 7.0.2, setPath in @rvf/set-get (used by @rvf/core to flatten incoming form data into a nested object) does not block the keys __pr…
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High 8.3
Velocity.js: Prototype Pollution in #set path assignment
Velocity.js is a JavaScript implementation of the Apache Velocity template engine. In 2.1.5 and earlier, a prototype pollution vulnerability was discovered in velocityjs. This issue occurs during the processing of #set directives in Velocity templates. If an …
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Medium 4.3
Prototype pollution in csv parsing
Prototype pollution in csv parsing logic during import can lead to untrusted file paths (but not arguments) entering shell.openExternal after specific user behavior leading to "1-click" command execution.
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High 8.2
jsondiffpatch patch APIs are vulnerable to prototype pollution
Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpatch.patch() and jsondiffpatch/formatters/jsonpatch.patch() APIs. An attacker can perform prototype pollution by supplying crafted delta or JSON Patch do…
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Critical 10.0
vm2: Sandbox escape
vm2 is an open source vm/sandbox for Node.js. From 3.9.6 to 3.10.5, vm2's bridge exposes mutable proxies for real host-realm intrinsic prototypes and then forwards sandbox writes into the underlying host objects with otherReflectSet() and otherReflectDefinePr…
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Medium 5.3
protobufjs: Prototype injection in generated message constructors
protobufjs compiles protobuf definitions into JavaScript (JS) functions. Prior to 7.5.6 and 8.0.2, protobufjs generated message constructors copied enumerable properties from a provided properties object without filtering the __proto__ key. If an application …
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High 8.1
protobufjs: Code generation gadget after prototype pollution
protobufjs compiles protobuf definitions into JavaScript (JS) functions. Prior to 7.5.6 and 8.0.2, protobufjs used plain objects with inherited prototypes for internal type lookup tables used by generated encode and decode functions. If Object.prototype had a…
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High 7.5
protobufjs: Process-wide denial of service through unsafe option paths
protobufjs compiles protobuf definitions into JavaScript (JS) functions. Prior to 7.5.6 and 8.0.2, protobufjs allowed certain schema option paths to traverse through inherited object properties while applying options. A crafted protobuf schema or JSON descrip…
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High 7.5CVE-2026-8161 Public exploit
multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception
multiparty@4.2.3 and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as __proto__, constructor, or toString, t…
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High 7.5
@theecryptochad/merge-guard has Prototype Pollution in its deepMerge() function
## Summary `@theecryptochad/merge-guard` versions prior to 1.0.1 are vulnerable to Prototype Pollution via the `deepMerge()` function. An attacker who controls the source object can inject `__proto__` keys that mutate `Object.prototype`, affecting all objects…
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High 8.6
Prototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parameters
18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Versions prior to 3.9.3 allow an unauthenticated HTTP client to pollute Object.prototype in the Node.js process hosting the middleware, vi…
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High 7.4
Axios: Prototype pollution read-side gadgets in HTTP adapter allow credential injection and request hijacking
Axios is a promise based HTTP client for the browser and Node.js. From version 1.0.0 to before version 1.15.2, fFive config properties (auth, baseURL, socketPath, beforeRedirect, and insecureHTTPParser) in the HTTP adapter are read via direct property access …
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Critical 9.8
query-parser-string is vulnerable to Prototype Pollution
NPM package query-parser-string 1.0.0 is vulnerable to Prototype Pollution. The package does not properly sanitize user supplied query parameters and merges them to the newly created object.
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Critical 9.8
parse-ini is vulnerable to Prototype Pollution in index.js()
npm package parse-ini v1.0.6 is vulnerable to Prototype Pollution in index.js().
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Medium 4.2
next-intl has prototype pollution with `experimental.messages.precompile` via attacker-controlled translation catalog keys
## Summary `setNestedProperty` in `packages/next-intl/src/extractor/utils.tsx` walks a dotted key path and assigns the final value without blocking the reserved keys `__proto__`, `constructor`, or `prototype`. When the next-intl Next.js plugin is configured w…
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Low 3.7
mcp-data-vis vulnerable to denial of service via unsanitized `select` key lookup on `Object.prototype` with `precompile: true`
## Summary `icu-minify`'s runtime formatter resolves `select` branches by looking up the runtime value as a plain property on a prototype-bearing object. When the value coerces to a key that exists on `Object.prototype` (e.g. `toString`, `__proto__`, `constru…
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Critical 9.4
n8n: XML Node Prototype Pollution to RCE
n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, an authenticated user with permission to create or modify workflows could achieve global prototype pollution via the XML Node leading to RCE when combined with…
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Critical 9.4CVE-2026-42231 Public exploit
n8n: Prototype Pollution in XML Webhook Body Parser Leads to RCE
n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, a flaw in the xml2js library used to parse XML request bodies in n8n's webhook handler allowed prototype pollution via a crafted XML payload. An authenticated …
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Medium 5.2
Evolver: Prototype Pollution via `Object.assign()` in mailbox store operations
Evolver is a GEP-powered self-evolving engine for AI agents. Prior to version 1.69.3, a prototype pollution vulnerability in the mailbox store module allows attackers to modify the behavior of all JavaScript objects by injecting malicious properties into Obje…
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Medium 4.8
Axios: Authentication Bypass via Prototype Pollution Gadget in `validateStatus` Merge Strategy
Axios is a promise based HTTP client for the browser and Node.js. Prior to 1.15.1 and 0.31.1, the Axios library is vulnerable to a Prototype Pollution "Gadget" attack that allows any Object.prototype pollution to silently suppress all HTTP error responses (40…
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Medium 6.5
Axios: Invisible JSON Response Tampering via Prototype Pollution Gadget in `parseReviver`
Axios is a promise based HTTP client for the browser and Node.js. From 1.0.0 to before 1.15.2, he Axios library is vulnerable to a Prototype Pollution "Gadget" attack that allows any Object.prototype pollution in the application's dependency tree to be escala…
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High 7.4
Axios: Header Injection via Prototype Pollution
Axios is a promise based HTTP client for the browser and Node.js. Prior to 1.15.1 and 0.31.1, a prototype pollution gadget exists in the Axios HTTP adapter (lib/adapters/http.js) that allows an attacker to inject arbitrary HTTP headers into outgoing requests.…
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High 7.4
Axios: Prototype Pollution Gadgets - Response Tampering, Data Exfiltration, and Request Hijacking
Axios is a promise based HTTP client for the browser and Node.js. Prior to 1.15.1 and 0.31.1, when Object.prototype has been polluted by any co-dependency with keys that axios reads without a hasOwnProperty guard, an attacker can (a) silently intercept and mo…
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Medium 6.9
DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Versions 3.0.1 through 3.3.3 are vulnerable to a prototype pollution-based XSS bypass. When an application uses `DOMPurify.sanitize()` with the default configuration (no `CUSTOM…
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High 7.3
1024bit extend-deep index.js prototype pollution
A vulnerability was determined in 1024bit extend-deep up to 0.1.6. The impacted element is an unknown function of the file index.js. This manipulation of the argument __proto__ causes improperly controlled modification of object prototype attributes. Remote e…
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High 7.3
brikcss merge prototype pollution
A vulnerability was determined in brikcss merge up to 1.3.0. This affects an unknown part. Executing a manipulation of the argument __proto__/constructor.prototype/prototype can lead to improperly controlled modification of object prototype attributes. The at…
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Medium 6.5
Mafintosh's protocol-buffers-schema is vulnerable to prototype pollution
JavaScript is vulnerable to prototype pollution in Mafintosh's protocol-buffers-schema Version 3.6.0, where an attacker may alter the application logic, bypass security checks, cause a DoS or achieve remote code execution.
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High 8.6
Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321)
Acrobat Reader versions 26.001.21411, 24.001.30360, 24.001.30362 and earlier are affected by an Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability that could result in arbitrary code execution in the contex…
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Medium 6.3
Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321)
Acrobat Reader versions 26.001.21411, 24.001.30360, 24.001.30362 and earlier are affected by an Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability that could result in arbitrary file system read in the cont…
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High 8.6
Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321)
Acrobat Reader versions 24.001.30356, 26.001.21367 and earlier are affected by an Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability that could result in arbitrary code execution in the context of the curre…
KEV Apr 13, 2026 -
Medium 5.6
LangSmith Client SDKs has Prototype Pollution in langsmith-sdk via Incomplete `__proto__` Guard in Internal lodash `set()`
LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. Prior to 0.5.18, the LangSmith JavaScript/TypeScript SDK (langsmith) contains an incomplete prototype pollution fix in its internally vendored lodash set() utility. The baseAssig…
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High 7.5
defu: Prototype pollution via `__proto__` key in defaults argument
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…
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Medium 6.5
lodash vulnerable to Prototype Pollution via array path bypass in `_.unset` and `_.omit`
The _.unset and _.omit functions in Lodash are vulnerable to prototype pollution. The fix for CVE-2025-13465 only guards against string key members, so an attacker can bypass the check by passing array-wrapped path segments. This allows deletion of properties…
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High 8.3
MikroORM has Prototype Pollution in Utils.merge
MikroORM is a TypeScript ORM for Node.js based on Data Mapper, Unit of Work and Identity Map patterns. Prior to versions 6.6.10 and 7.0.6, a prototype pollution vulnerability exists in the Utils.merge helper used internally by MikroORM when merging object str…
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Medium 4.8
Handlebars.js has a Prototype Method Access Control Gap via Missing __lookupSetter__ Blocklist Entry
## Summary The prototype method blocklist in `lib/handlebars/internal/proto-access.js` blocks `constructor`, `__defineGetter__`, `__defineSetter__`, and `__lookupGetter__`, but omits the symmetric `__lookupSetter__`. This omission is only exploitable when the…
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Medium 6.3
Locutus Prototype Pollution due to incomplete fix for CVE-2026-25521
Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Starting in version 2.0.39 and prior to version 3.0.25, a prototype pollution vulnerability exists in the `parse_str` function of the npm package locutus. An attacke…
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Medium 6.9
Locutus has Prototype Pollution via __proto__ Key Injection in unserialize()
Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Prior to version 3.0.25, the `unserialize()` function in `locutus/php/var/unserialize` assigns deserialized keys to plain objects via bracket notation without filter…