CVE-2024-53441: cookie-encrypter Bit Flipping Vulnerability

CVE-2024-53441 Overview

CVE-2024-53441 is a critical cryptographic vulnerability in the index.jsdecryptCookie function of the cookie-encrypter npm package version 1.0.1. This vulnerability allows attackers to execute a bit flipping attack, potentially enabling unauthorized modification of encrypted cookie data without knowledge of the encryption key. The flaw stems from the use of a broken or risky cryptographic algorithm (CWE-327), which fails to properly authenticate encrypted cookie values.

Critical Impact

Attackers can manipulate encrypted cookie contents through bit flipping, potentially bypassing authentication mechanisms, escalating privileges, or tampering with session data without detection.

Affected Products

• cookie-encrypter v1.0.1
• Applications using the decryptCookie function from cookie-encrypter
• Node.js web applications relying on cookie-encrypter for session management

Discovery Timeline

• 2024-12-09 - CVE-2024-53441 published to NVD
• 2024-12-12 - Last updated in NVD database

Technical Details for CVE-2024-53441

Vulnerability Analysis

This vulnerability exists in the decryptCookie function within index.js of the cookie-encrypter package. The core issue lies in the implementation of an encryption scheme that lacks proper integrity verification, making it susceptible to bit flipping attacks. In a bit flipping attack, an adversary can modify specific bits of the ciphertext, which results in predictable changes to the plaintext after decryption.

The vulnerability is classified under CWE-327 (Use of a Broken or Risky Cryptographic Algorithm), indicating that the cryptographic implementation does not provide adequate protection against tampering. When encryption modes like CBC (Cipher Block Chaining) are used without authenticated encryption (such as AEAD modes), the ciphertext can be manipulated without detection.

Root Cause

The root cause of this vulnerability is the absence of cryptographic integrity verification (authentication) on encrypted cookie values. The decryptCookie function decrypts data without validating that the ciphertext has not been tampered with. This allows an attacker who can intercept and modify encrypted cookies to alter specific bytes in a controlled manner, resulting in modified plaintext values after decryption.

Proper implementations should use authenticated encryption modes (such as AES-GCM) or include a separate HMAC to verify data integrity before decryption.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker positioned to intercept and modify HTTP traffic (via man-in-the-middle, XSS, or other cookie exfiltration techniques) can:

1. Capture encrypted cookie values from HTTP responses or browser storage
2. Apply targeted bit modifications to the ciphertext
3. Submit the modified cookie back to the server
4. Exploit the predictable plaintext changes to bypass security controls

For example, if a cookie contains a serialized user role such as user, an attacker could potentially flip specific bits to change it to admin without knowing the encryption key. Technical details and a proof-of-concept demonstrating this attack are available in the GitHub Gist PoC Repository.

Detection Methods for CVE-2024-53441

Indicators of Compromise

• Unusual cookie values that fail application-level validation after decryption
• Repeated authentication or authorization anomalies for specific user sessions
• Log entries indicating decryption succeeded but parsed data is malformed or unexpected
• Session hijacking or privilege escalation events without corresponding authentication logs

Detection Strategies

• Implement application-layer logging to capture decrypted cookie values that fail schema validation
• Monitor for patterns of repeated failed authorization checks from the same session
• Deploy web application firewalls (WAF) with rules to detect cookie tampering patterns
• Use SentinelOne Singularity to detect suspicious runtime behavior in Node.js applications

Monitoring Recommendations

• Enable verbose logging for cookie decryption operations in affected applications
• Set up alerts for authorization bypass attempts or unexpected privilege changes
• Monitor dependency scanning tools for applications using cookie-encrypter v1.0.1
• Review access logs for sessions exhibiting inconsistent permission states

How to Mitigate CVE-2024-53441

Immediate Actions Required

• Audit all applications using cookie-encrypter v1.0.1 to identify exposure
• Replace cookie-encrypter with a library implementing authenticated encryption (AEAD)
• Implement HMAC verification for all encrypted cookie values as an interim measure
• Rotate encryption keys and invalidate existing sessions after implementing fixes

Patch Information

As of the last NVD update on 2024-12-12, no official patch has been released for cookie-encrypter. Organizations should consider migrating to alternative cookie encryption solutions that implement authenticated encryption modes such as AES-GCM. For detailed technical analysis of the vulnerability, refer to the Reboux CVE-2024-53441 Analysis.

Workarounds

• Implement server-side HMAC validation before decrypting any cookie values
• Migrate to an authenticated encryption library such as iron or Node.js native crypto with GCM mode
• Add server-side session validation that cross-references cookie data with database-stored session state
• Deploy additional application-layer integrity checks for sensitive cookie fields

# Example: Switching to authenticated encryption in Node.js
# Replace cookie-encrypter with native crypto using AES-256-GCM
# This provides both confidentiality and integrity protection

npm uninstall cookie-encrypter
# Implement custom solution using crypto.createCipheriv with 'aes-256-gcm'
# Ensure auth tags are generated and verified during encryption/decryption