CVE-2023-31582: Jose4j Low Iteration Count Vulnerability

CVE-2023-31582 Overview

CVE-2023-31582 is a cryptographic vulnerability in jose4j, a popular Java library for JSON Web Tokens (JWT) and JSON Object Signing and Encryption (JOSE). The vulnerability allows attackers to set an insecure Password-Based Key Derivation Function 2 (PBKDF2) iteration count of 1000 or less, significantly weakening the cryptographic protections designed to defend against brute-force attacks on password-derived keys.

Critical Impact

Applications using jose4j versions before v0.9.3 may be vulnerable to cryptographic attacks due to insufficient entropy in password-based encryption, potentially allowing attackers to compromise encrypted JWT tokens.

Affected Products

• jose4j_project jose4j versions prior to v0.9.3

Discovery Timeline

• 2023-10-25 - CVE-2023-31582 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-31582

Vulnerability Analysis

This vulnerability falls under CWE-331 (Insufficient Entropy), which describes situations where the random values used in cryptographic operations do not contain enough unpredictability to resist computational attacks. In the context of jose4j, the library allows Password-Based Encryption (PBE) operations to use dangerously low PBKDF2 iteration counts.

PBKDF2 is a key derivation function that applies a pseudorandom function (typically HMAC-SHA1 or HMAC-SHA256) to a password along with a salt value and repeats the process many times to produce a derived key. The iteration count is a critical security parameter that directly impacts the computational cost required to brute-force the password. Modern security guidelines recommend iteration counts of at least 310,000 for PBKDF2-HMAC-SHA256 (as per OWASP 2023 recommendations).

By allowing iteration counts as low as 1000 or less, jose4j enables configurations that can be trivially attacked using commodity hardware, rendering the password-based encryption effectively useless against determined adversaries.

Root Cause

The root cause of this vulnerability is the lack of validation or enforcement of minimum iteration count values in the jose4j library's password-based encryption implementation. The library accepted user-supplied iteration count parameters without verifying that they meet minimum security thresholds. This design flaw allows developers to inadvertently (or maliciously) configure insecure cryptographic parameters.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker who intercepts or obtains encrypted JWT tokens protected with low PBKDF2 iteration counts can perform offline brute-force attacks against the password. With iteration counts of 1000 or less, modern GPUs can test millions of password candidates per second, making it feasible to crack weak to moderately strong passwords in a practical timeframe.

The attack scenario typically involves:

1. An attacker captures encrypted JWE (JSON Web Encryption) tokens from network traffic or storage
2. The attacker identifies that the tokens use PBE with low iteration counts
3. Using password cracking tools, the attacker brute-forces the encryption password
4. Once the password is recovered, the attacker can decrypt all tokens encrypted with that password, potentially exposing sensitive authentication data, session information, or other confidential payloads

For detailed technical analysis, refer to the Bitbucket Issue Report and GitHub JWT Issues Documentation.

Detection Methods for CVE-2023-31582

Indicators of Compromise

• JWE tokens containing PBES2 algorithms with unusually low iteration counts in the header (e.g., "p2c": 1000 or lower)
• Anomalous patterns of failed decryption attempts followed by successful authentication using recovered credentials
• Evidence of password cracking tools or GPU-accelerated computation targeting JWT tokens in forensic analysis

Detection Strategies

• Implement dependency scanning in CI/CD pipelines to identify jose4j versions prior to v0.9.3
• Conduct code reviews to identify any explicit configuration of PBKDF2 iteration counts below recommended thresholds
• Use software composition analysis (SCA) tools to maintain an inventory of cryptographic library versions
• Monitor application logs for JWT processing errors that may indicate tampering or attack attempts

Monitoring Recommendations

• Enable detailed logging of JWT encryption and decryption operations, including algorithm parameters
• Deploy network monitoring to detect suspicious patterns of token capture or replay
• Implement alerting for authentication anomalies that may indicate credential compromise from decrypted tokens
• Regularly audit cryptographic configurations in applications using jose4j or similar JWT libraries

How to Mitigate CVE-2023-31582

Immediate Actions Required

• Upgrade jose4j to version v0.9.3 or later, which enforces minimum iteration count requirements
• Audit existing applications to identify any explicit configuration of low PBKDF2 iteration counts
• Review and update any JWE tokens that were encrypted using weak iteration counts—consider re-encrypting with secure parameters
• If upgrading is not immediately possible, implement application-level validation to reject iteration counts below 310,000

Patch Information

The jose4j development team addressed this vulnerability in version v0.9.3. The fix includes validation logic that prevents the use of insecure PBKDF2 iteration counts. Organizations should update their dependency configurations to use the patched version. For Maven users, update the jose4j dependency in pom.xml to specify version 0.9.3 or later.

For more information, see the Bitbucket Issue Report.

Workarounds

• If immediate upgrade is not feasible, implement wrapper functions that validate iteration counts before calling jose4j encryption methods
• Configure web application firewalls (WAF) to inspect and reject JWE tokens with insecure p2c (PBES2 count) values
• Consider migrating to asymmetric key encryption (RSA or EC) for JWE operations, which eliminates the dependency on password-based key derivation
• Implement strong password policies for any passwords used in PBE operations to increase resistance to brute-force attacks even with suboptimal iteration counts

# Example Maven dependency update to patched version
# Update pom.xml to use jose4j v0.9.3 or later
# <dependency>
#     <groupId>org.bitbucket.b_c</groupId>
#     <artifactId>jose4j</artifactId>
#     <version>0.9.3</version>
# </dependency>