no-buffer-overread

Keywords: buffer overread, CWE-126, out-of-bounds, memory safety, security, Node.js

CWE: CWE-693
OWASP Mobile: OWASP Mobile Top 10

Detects buffer access beyond bounds. This rule is part of eslint-plugin-node-security.

💼 This rule is set to error in the recommended config.

Quick Summary

Aspect	Details
CWE Reference	CWE-126 (Buffer Over-read)
Severity	High (CVSS 7.5)
Auto-Fix	💡 Suggestions available
Category	Security

Vulnerability and Risk

Vulnerability: Buffer over-read occurs when a program reads from a buffer (memory) past the buffer's boundary or before its beginning.

Risk: This can lead to the exposure of sensitive information residing in adjacent memory locations (Information Leakage), cause the application to crash (Denial of Service), or result in unexpected application behavior.

Rule Details

Buffer overread occurs when reading from buffers beyond their allocated length. This can lead to:

Information disclosure (reading adjacent memory)
Application crashes
Security vulnerabilities like Heartbleed
Undefined behavior

Why This Matters

Issue	Impact	Solution
📤 Info Leak	Sensitive data exposure	Validate buffer indices
💥 Crash	Denial of service	Check bounds before access
🔓 Security Bypass	Memory corruption	Use safe buffer methods

Examples

❌ Incorrect

// Reading beyond buffer length
const buf = Buffer.from('hello');
const byte = buf[10]; // Out of bounds!

// User-controlled index without validation
const index = parseInt(req.query.index);
const value = buffer[index]; // Potentially negative or too large!

// Slice without bounds checking
const data = buffer.slice(offset, offset + length);
// No validation that offset + length <= buffer.length

// readUInt32LE without bounds check
const value = buf.readUInt32LE(userOffset);
// Could read past end of buffer

✅ Correct

if (index >= 0 && index < buffer.length) { const byte = buffer[index]; }

Configuration

{
  rules: {
    'node-security/no-buffer-overread': ['error', {
      bufferMethods: ['readUInt8', 'readUInt16LE', 'readUInt32LE', 'slice'],
      boundsCheckFunctions: ['validateIndex', 'checkBounds'],
      bufferTypes: ['Buffer', 'Uint8Array', 'ArrayBuffer']
    }]
  }
}

Options

Option	Type	Default	Description
`bufferMethods`	`string[]`	`['readUInt8', 'slice']`	Buffer methods to check
`boundsCheckFunctions`	`string[]`	`['validateIndex']`	Bounds checking functions
`bufferTypes`	`string[]`	`['Buffer', 'Uint8Array']`	Buffer types to monitor

Error Message Format

🔒 CWE-126 OWASP:A06-Vulnerable CVSS:7.5 | Buffer Overread | HIGH [SOC2,PCI-DSS]
   Fix: Add bounds check before buffer access | https://nodejs.org/api/buffer.html

Known False Negatives

The following patterns are not detected due to static analysis limitations:

Values from Variables

Why: Values stored in variables are not traced.

// ❌ NOT DETECTED - Value from variable
const value = userInput;
dangerousOperation(value);

Mitigation: Validate all user inputs.

Wrapper Functions

Why: Custom wrappers not recognized.

// ❌ NOT DETECTED - Wrapper
myWrapper(userInput); // Uses dangerous API internally

Mitigation: Apply rule to wrapper implementations.

Dynamic Invocation

Why: Dynamic calls not analyzed.

// ❌ NOT DETECTED - Dynamic
obj[method](userInput);

Mitigation: Avoid dynamic method invocation.