Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

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 current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.Show less

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 baseAssignValue() function only guards against the __proto__ key, but fails to prevent traversal via constructor.prototype. This allows an attacker who controls keys in data processed by the createAnonymizer() API to pollute Object.prototype, affecting all objects in the Node.js process. This vulnerability is fixed in 0.5.18.Show less

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.Show less

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 from built-in prototypes such as Object.prototype, Number.prototype, and String.prototype. The issue permits deletion of prototype properties but does not allow overwriting their original behavior. The issue is patched from 4.18.0 to 4.18.1 depending on the package: lodash, lodash-es, and lodash-amd in 4.18.1, and the standalone lodash.unset and lodash.omit packages in 4.18.0.Show less

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 structures. The function did not prevent special keys such as __proto__, constructor, or prototype, allowing attacker-controlled input to modify the JavaScript object prototype when merged. This issue has been patched in versions 6.6.10 and 7.0.6.Show less

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 attacker can pollute `Object.prototype` by overriding `RegExp.prototype.test` and then passing a crafted query string to `parse_str`, bypassing the prototype pollution guard. This vulnerability stems from an incomplete fix for CVE-2026-25521. The CVE-2026-25521 patch replaced the `String.prototype.includes()`-based guard with a `RegExp.prototype.test()`-based guard. However, `RegExp.prototype.test` is itself a writable prototype method that can be overridden, making the new guard bypassable in the same way as the original — trading one hijackable built-in for another. Version 3.0.25 contains an updated fix.Show less

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 filtering the `__proto__` key. When a PHP serialized payload contains `__proto__` as an array or object key, JavaScript's `__proto__` setter is invoked, replacing the deserialized object's prototype with attacker-controlled content. This enables property injection, for...in propagation of injected properties, and denial of service via built-in method override. This is distinct from the previously reported prototype pollution in `parse_str` (GHSA-f98m-q3hr-p5wq, GHSA-rxrv-835q-v5mh) — `unserialize` is a different function with no mitigation applied. Version 3.0.25 patches the issue.Show less

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `resolvePartial()` in the Handlebars runtime resolves partial names via a plain property lookup on `options.partials` without guarding against prototype-chain traversal. When `Object.prototype` has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered without HTML escaping, resulting in reflected or stored XSS. Version 4.7.9 fixes the issue. Some workarounds are available. Apply `Object.freeze(Object.prototype)` early in application startup to prevent prototype pollution. Note: this may break other libraries, and/or use the Handlebars runtime-only build (`handlebars/runtime`), which does not compile templates and reduces the attack surface.Show less

Picomatch is a glob matcher written JavaScript. Versions prior to 4.0.4, 3.0.2, and 2.3.2 are vulnerable to a method injection vulnerability affecting the `POSIX_REGEX_SOURCE` object. Because the object inherits from `Object.prototype`, specially crafted POSIX bracket expressions (e.g., `[[:constructor:]]`) can reference inherited method names. These methods are implicitly converted to strings and injected into the generated regular expression. This leads to incorrect glob matching behavior (integrity impact), where patterns may match unintended filenames. The issue does not enable remote code execution, but it can cause security-relevant logic errors in applications that rely on glob matching for filtering, validation, or access control. All users of affected `picomatch` versions that process untrusted or user-controlled glob patterns are potentially impacted. This issue is fixed in picomatch 4.0.4, 3.0.2 and 2.3.2. Users should upgrade to one of these versions or later, depending on their supported release line. If upgrading is not immediately possible, avoid passing untrusted glob patterns to picomatch. Possible mitigations include sanitizing or rejecting untrusted glob patterns, especially those containing POSIX character classes like `[[:...:]]`; avoiding the use of POSIX bracket expressions if user input is involved; and manually patching the library by modifying `POSIX_REGEX_SOURCE` to use a null prototype.Show less

n8n is an open source workflow automation platform. Prior to versions 2.14.1, 2.13.3, and 1.123.27, an authenticated user with permission to create or modify workflows could exploit a prototype pollution vulnerability in the XML and the GSuiteAdmin nodes. By supplying a crafted parameters as part of node configuration, an attacker could write attacker-controlled values onto `Object.prototype`. An attacker could use this prototype pollution to achieve remote code execution on the n8n instance. The issue has been fixed in n8n versions 2.14.1, 2.13.3, and 1.123.27. Users should upgrade to one of these versions or later to remediate the vulnerability. If upgrading is not immediately possible, administrators should consider the following temporary mitigations: Limit workflow creation and editing permissions to fully trusted users only, and/or disable the XML node by adding `n8n-nodes-base.xml` to the `NODES_EXCLUDE` environment variable. These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.Show less

flatted is a circular JSON parser. Prior to version 3.4.2, the parse() function in flatted can use attacker-controlled string values from the parsed JSON as direct array index keys, without validating that they are numeric. Since the internal input buffer is a JavaScript Array, accessing it with the key "__proto__" returns Array.prototype via the inherited getter. This object is then treated as a legitimate parsed value and assigned as a property of the output object, effectively leaking a live reference to Array.prototype to the consumer. Any code that subsequently writes to that property will pollute the global prototype. This issue has been patched in version 3.4.2.Show less

Qwik is a performance-focused JavaScript framework. Versions prior to 1.19.2 improperly inferred arrays from dotted form field names during FormData parsing. By submitting mixed array-index and object-property keys for the same path, an attacker could cause user-controlled properties to be written onto values that application code expected to be arrays. When processing application/x-www-form-urlencoded or multipart/form-data requests, Qwik City converted dotted field names (e.g., items.0, items.1) into nested structures. If a path was interpreted as an array, additional attacker-supplied keys on that path—such as items.toString, items.push, items.valueOf, or items.length—could alter the resulting server-side value in unexpected ways, potentially leading to request handling failures, denial of service through malformed array state or oversized lengths, and type confusion in downstream code. This issue was fixed in version 1.19.2.Show less

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.24 and 8.6.47, remote clients can crash the Parse Server process by calling a cloud function endpoint with a crafted function name that traverses the JavaScript prototype chain of a registered cloud function handler, causing a stack overflow. The fix in versions 9.6.0-alpha.24 and 8.6.47 restricts property lookups during cloud function name resolution to own properties only, preventing prototype chain traversal from stored function handlers. There is no known workaround.Show less

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.20 and 8.6.44, an attacker can bypass the default request keyword denylist protection and the class-level permission for adding fields by sending a crafted request that exploits prototype pollution in the deep copy mechanism. This allows injecting fields into class schemas that have field addition locked down, and can cause permanent schema type conflicts that cannot be resolved even with the master key. In 9.6.0-alpha.20 and 8.6.44, the vulnerable third-party deep copy library has been replaced with a built-in deep clone mechanism that handles prototype properties safely, allowing the existing denylist check to correctly detect and reject the prohibited keyword. No known workarounds are available.Show less

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, an Elysia cookie can be overridden by prototype pollution , eg. `__proto__`. This issue is patched in 1.4.27. As a workaround, use t.Cookie validation to enforce validation value and/or prevent iterable over cookie if possible.Show less

OpenClaw versions prior to 2026.2.21 accept prototype-reserved keys in runtime /debug set override object values, allowing prototype pollution attacks. Authorized /debug set callers can inject __proto__, constructor, or prototype keys to manipulate object prototypes and bypass command gate restrictions.Show less

A vulnerability was found in Lagom WHMCS Template up to 2.3.7. Impacted is an unknown function of the component Datatables. The manipulation results in improperly controlled modification of object prototype attributes. It is possible to launch the attack remotely. The exploit has been made public and could be used. The vendor was contacted early about this disclosure but did not respond in any way.Show less

Apollo Federation is an architecture for declaratively composing APIs into a unified graph. Prior to 2.9.6, 2.10.5, 2.11.6, 2.12.3, and 2.13.2, a vulnerability exists in query plan execution within the gateway that may allow pollution of Object.prototype in certain scenarios. A malicious client may be able to pollute Object.prototype in gateway directly by crafting operations with field aliases and/or variable names that target prototype-inheritable properties. Alternatively, if a subgraph were to be compromised by a malicious actor, they may be able to pollute Object.prototype in gateway by crafting JSON response payloads that target prototype-inheritable properties. This vulnerability is fixed in 2.9.6, 2.10.5, 2.11.6, 2.12.3, and 2.13.2.Show less

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.Show less

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 8.6.13 and 9.5.1-alpha.2, an unauthenticated attacker can crash the Parse Server process by calling a Cloud Function endpoint with a prototype property name as the function name. The server recurses infinitely, causing a call stack size error that terminates the process. Other prototype property names bypass Cloud Function dispatch validation and return HTTP 200 responses, even though no such Cloud Functions are defined. The same applies to dot-notation traversal. All Parse Server deployments that expose the Cloud Function endpoint are affected. This vulnerability is fixed in 8.6.13 and 9.5.1-alpha.2.Show less