EUVD-2026-46260
GHSA-x7j8-49r8-mr43
Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploitation needs the app to feed untrusted input to objDeepCopy plus a gadget, so AC:H; no auth (PR:N); primary impact is prototype integrity (I:H) with possible DoS (A:L) and no confidentiality loss.
Primary rating from Vendor (https://github.com/nevware21/ts-utils).
CVSS VectorVendor: https://github.com/nevware21/ts-utils
Lifecycle Timeline
5Blast Radius
ecosystem impact- 1 npm packages depend on @nevware21/ts-utils (1 direct, 0 indirect)
Ecosystem-wide dependent count for version 0.14.0.
DescriptionCVE.org
Summary
The _copyProps function in lib/src/object/copy.ts uses for...in to iterate over source object properties without an Object.hasOwnProperty check, and does not filter dangerous keys (__proto__, constructor, prototype). This allows an attacker to pollute the prototype chain of all objects in the application.
Details
In _copyProps() (copy.ts lines 186-191), the code iterates all enumerable properties including inherited ones and dangerous keys like __proto__. Any object with a __proto__ key (e.g., from untrusted JSON input) will overwrite the target's prototype.
PoC
const malicious = JSON.parse('{"__proto__": {"polluted": true}}');
objDeepCopy(malicious);
console.log({}.polluted); // trueSuggested Fix
Add objHasOwnProperty check and filter __proto__, constructor, prototype keys.
AnalysisAI
Prototype pollution in the @nevware21/ts-utils npm library (versions <= 0.13.0) lets an attacker who can influence an object passed to objDeepCopy() or objCopyProps() inject a __proto__ (or constructor/prototype) key that overwrites Object.prototype for the entire application. The flaw stems from _copyProps() in lib/src/object/copy.ts iterating with for...in and no hasOwnProperty guard, so parsing untrusted JSON and deep-copying it is enough to poison every object. A working proof-of-concept is published in the GHSA advisory, though EPSS is very low (0.06%) and the issue is not on CISA KEV, so publicly available exploit code exists but no active exploitation is confirmed.
Technical ContextAI
The affected component is the TypeScript utility library @nevware21/ts-utils (npm package pkg:npm/@nevware21/ts-utils), specifically its object copy helpers objDeepCopy and objCopyProps backed by the internal _copyProps function. The root cause is CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes, i.e. prototype pollution): _copyProps uses a JavaScript for...in loop, which walks both own and inherited enumerable properties and does not distinguish the special __proto__ accessor. Without an Object.hasOwnProperty / objHasOwnProperty filter and without excluding the dangerous keys __proto__, constructor, and prototype, assigning a source property named __proto__ mutates the target object's prototype rather than setting an own property. Because JavaScript objects share Object.prototype, a single polluting copy propagates to all objects created in the running process, potentially altering control-flow-relevant defaults, enabling denial of service, or feeding downstream gadgets.
RemediationAI
Vendor-released patch: 0.14.0 - upgrade @nevware21/ts-utils to >= 0.14.0, which adds objHasOwnProperty checks and filters the __proto__, constructor, and prototype keys (see advisory https://github.com/nevware21/ts-utils/security/advisories/GHSA-x7j8-49r8-mr43 and fix commit https://github.com/nevware21/ts-utils/commit/5e887f4e2fbee7160c8f501634c45e6a229e83bb). Because the package is frequently a transitive dependency, run npm ls @nevware21/ts-utils and update or override the resolved version (npm overrides / yarn resolutions) so nested copies are also bumped. If an immediate upgrade is not possible, apply compensating controls in the calling code: avoid passing unsanitized JSON directly into objDeepCopy/objCopyProps, strip or reject any incoming object containing a __proto__/constructor/prototype key before copying, and consider Object.freeze(Object.prototype) at startup to block prototype mutation (trade-off: this can break libraries that legitimately extend prototypes and must be tested). Parsing untrusted input with a reviver that drops dangerous keys, or using Map/null-prototype objects for attacker-controlled data, further reduces exposure until the patched version is deployed.
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External POC / Exploit Code
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