CVE-2023-27987: Apache Linkis Auth Bypass Vulnerability

CVE-2023-27987 Overview

A critical weak cryptographic vulnerability has been discovered in Apache Linkis versions 1.3.1 and earlier. The vulnerability stems from the default token generated by the Linkis Gateway deployment being too simple, making it easy for attackers to obtain and use this token to perform unauthorized actions. The token generation rules lack sufficient randomness, creating a predictable authentication mechanism that can be exploited remotely.

Critical Impact

Attackers can obtain the default authentication token without authorization, potentially gaining unauthorized access to the Linkis Gateway with high confidentiality and integrity impact.

Affected Products

• Apache Linkis versions 1.3.1 and earlier
• Apache Linkis Gateway component
• All deployments using default token configurations

Discovery Timeline

• 2023-04-10 - CVE-2023-27987 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-27987

Vulnerability Analysis

This vulnerability is classified under CWE-326 (Inadequate Encryption Strength), indicating that the cryptographic protection mechanism employed by the Linkis Gateway is insufficiently robust. The default token generation mechanism in Apache Linkis Gateway lacks proper randomization, resulting in predictable token values that attackers can easily guess or brute-force. When an attacker successfully obtains the default token, they can bypass authentication controls and perform actions as if they were a legitimate authorized user.

The attack can be executed remotely over the network without requiring any user interaction or prior authentication. This makes the vulnerability particularly dangerous for internet-facing Linkis deployments. Successful exploitation results in high impact to both confidentiality and integrity, as attackers can access sensitive data and potentially modify system configurations or data.

Root Cause

The root cause of this vulnerability lies in the inadequate token generation algorithm used by the Linkis Gateway during deployment. The token generation process does not incorporate sufficient random values, resulting in tokens that are predictable or easily guessable. This design flaw violates fundamental security principles for authentication tokens, which should be cryptographically random and unpredictable.

Attack Vector

The attack vector is network-based, requiring the attacker to have network access to the Linkis Gateway endpoint. The exploitation process involves identifying or guessing the default token value used by the Linkis Gateway, then using this token to authenticate and gain unauthorized access to the system. No special privileges or user interaction are required to execute this attack.

An attacker would typically probe the Linkis Gateway endpoint, attempt to use known default or weak token values, and upon successful token validation, gain access to protected resources and functionality. The simplicity of the default token makes enumeration attacks highly effective.

Detection Methods for CVE-2023-27987

Indicators of Compromise

• Unusual authentication attempts against the Linkis Gateway using default or predictable token values
• Multiple failed authentication attempts followed by a successful login from the same source
• Unexpected API calls or administrative actions from unrecognized IP addresses
• Anomalous patterns in Linkis Gateway access logs indicating token enumeration attempts

Detection Strategies

• Monitor Linkis Gateway authentication logs for patterns indicative of brute-force or enumeration attacks
• Implement rate limiting on authentication endpoints to detect and block rapid token guessing attempts
• Deploy network intrusion detection rules to identify traffic patterns associated with token exploitation
• Audit current token configurations to identify deployments still using default values

Monitoring Recommendations

• Enable verbose logging on Linkis Gateway authentication events
• Configure alerting for authentication failures exceeding defined thresholds
• Implement continuous monitoring for unauthorized access patterns in Linkis administrative functions
• Review access logs regularly for signs of unauthorized token usage

How to Mitigate CVE-2023-27987

Immediate Actions Required

• Upgrade Apache Linkis to version 1.3.2 or later immediately
• Modify the default token value to a cryptographically strong, random value
• Review and restrict network access to Linkis Gateway endpoints
• Audit access logs for any signs of prior exploitation

Patch Information

Apache has addressed this vulnerability in Linkis version 1.3.2. The patch improves the token generation algorithm to include proper random values, making tokens significantly harder to predict or brute-force. Users should upgrade to version 1.3.2 or later and regenerate their authentication tokens. For detailed guidance on token authorization configuration, refer to the Apache Linkis Token Authorization Documentation. Additional information is available in the Apache Mailing List Discussion and the OpenWall OSS Security Update.

Workarounds

• If immediate upgrade is not possible, manually replace the default token with a cryptographically strong random value
• Implement network-level access controls to restrict access to the Linkis Gateway to trusted IP ranges only
• Deploy a Web Application Firewall (WAF) to add an additional layer of authentication protection
• Consider disabling the Linkis Gateway if it is not actively required until the patch can be applied

# Configuration example
# Replace default token with a cryptographically strong random value
# Generate a secure random token using openssl
openssl rand -hex 32

# Update the Linkis Gateway configuration with the new token
# Refer to Apache Linkis documentation for specific configuration file locations
# Example: linkis-gateway.properties
# token.value=<your_new_secure_random_token>