CVE-2024-32007: Apache CXF JOSE DOS Vulnerability

CVE-2024-32007 Overview

CVE-2024-32007 is an improper input validation vulnerability affecting the Apache CXF JOSE (JavaScript Object Signing and Encryption) code. The vulnerability exists in the handling of the p2c (PBES2 iteration count) parameter, which allows an attacker to specify an arbitrarily large value in a token. When the application processes a token with an excessive p2c value, it can trigger a denial of service condition by consuming excessive computational resources during password-based encryption operations.

Critical Impact

Attackers can exploit this vulnerability remotely without authentication to cause denial of service by sending specially crafted tokens with large p2c parameter values, potentially making applications unavailable to legitimate users.

Affected Products

• Apache CXF versions before 4.0.5
• Apache CXF versions before 3.6.4
• Apache CXF versions before 3.5.9

Discovery Timeline

• 2024-07-19 - CVE CVE-2024-32007 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-32007

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-20) in the Apache CXF JOSE implementation. The JOSE specification defines the p2c parameter as the PBES2 (Password-Based Encryption Scheme 2) iteration count, which determines how many times the key derivation function is applied during encryption and decryption operations. Without proper bounds checking, an attacker can supply an extremely large iteration count value, causing the system to perform excessive cryptographic computations.

The attack is particularly impactful because it requires no authentication and can be executed remotely over the network. A single malicious request with an inflated p2c value can consume significant CPU resources, and sustained attacks can render the service unavailable to legitimate users.

Root Cause

The root cause is the absence of upper bound validation on the p2c parameter in the JOSE token processing code. The PBES2 iteration count is intended to add computational cost to deter brute-force attacks against encrypted content, but without a maximum limit, this security feature becomes an attack vector. The application accepts arbitrary p2c values from untrusted input (the token), allowing attackers to dictate the computational cost of token processing.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An attacker crafts a JOSE token (JWE - JSON Web Encryption) containing a maliciously large p2c parameter value in the token header. When the target Apache CXF application attempts to decrypt or validate this token, the key derivation function iterates the specified number of times, consuming CPU resources proportional to the p2c value.

The attack can be executed against any endpoint that processes JOSE tokens, including REST API authentication endpoints, SSO implementations, and web services using encrypted tokens. Multiple concurrent requests can amplify the denial of service effect.

Detection Methods for CVE-2024-32007

Indicators of Compromise

• Unusual CPU spikes on application servers processing JOSE/JWE tokens
• Increased response times or timeouts on authentication-related endpoints
• Log entries showing token processing failures after extended delays
• Abnormally large p2c values in incoming JWE token headers (typically legitimate values are in the thousands, not millions)

Detection Strategies

• Monitor CPU utilization patterns on services handling JOSE token processing
• Implement request logging that captures JWE header parameters for analysis
• Set up alerting for authentication endpoint response time anomalies
• Review web application firewall logs for unusually large JSON payloads in token fields

Monitoring Recommendations

• Configure application performance monitoring (APM) to track JOSE token processing latency
• Establish baseline metrics for normal p2c values in your environment and alert on deviations
• Monitor thread pool exhaustion in Java application servers running Apache CXF
• Implement rate limiting on endpoints that accept JOSE tokens to mitigate bulk attack attempts

How to Mitigate CVE-2024-32007

Immediate Actions Required

• Upgrade Apache CXF to version 4.0.5, 3.6.4, or 3.5.9 or later depending on your version branch
• If immediate upgrade is not possible, implement rate limiting on endpoints processing JOSE tokens
• Consider implementing a Web Application Firewall (WAF) rule to inspect and limit p2c parameter values
• Review and audit all endpoints that accept JWE tokens for exposure to this vulnerability

Patch Information

Apache has released security patches addressing this vulnerability. Users should upgrade to the following versions:

• For the 4.x branch: upgrade to 4.0.5 or later
• For the 3.6.x branch: upgrade to 3.6.4 or later
• For the 3.5.x branch: upgrade to 3.5.9 or later

For detailed patch information, refer to the Apache Mailing List Discussion. Additional vendor guidance is available in the NetApp Security Advisory ntap-20240808-0009.

Workarounds

• Implement request timeout limits on token processing operations to prevent long-running computations
• Deploy rate limiting on authentication and token validation endpoints
• Add input validation at the application or WAF level to reject tokens with p2c values exceeding reasonable thresholds (e.g., values above 310,000 should be scrutinized)
• Consider temporarily disabling PBES2-based encryption if not required for your use case

# Example Maven dependency update for Apache CXF 4.x
# Update pom.xml to use patched version:
# <dependency>
#     <groupId>org.apache.cxf</groupId>
#     <artifactId>cxf-core</artifactId>
#     <version>4.0.5</version>
# </dependency>