CVE-2026-40945: Oxia Information Disclosure Vulnerability

CVE-2026-40945 Overview

CVE-2026-40945 is a sensitive information exposure vulnerability in Oxia, a metadata store and coordination system. When OIDC authentication fails, the full bearer token is logged at DEBUG level in plaintext. If debug logging is enabled in production environments, JWT tokens are exposed in application logs and any connected log aggregation system, potentially allowing attackers to hijack authenticated sessions.

Critical Impact

Exposure of JWT bearer tokens in plaintext logs can lead to session hijacking, unauthorized access to protected resources, and potential lateral movement within systems using Oxia for coordination.

Affected Products

• Oxia versions prior to 0.16.2

Discovery Timeline

• 2026-04-21 - CVE CVE-2026-40945 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-40945

Vulnerability Analysis

This vulnerability falls under CWE-532 (Insertion of Sensitive Information into Log File). When Oxia processes OIDC authentication requests that fail validation, the system logs the complete bearer token at DEBUG log level without sanitization or redaction. This design flaw exposes sensitive authentication credentials to anyone with access to application logs.

The vulnerability is particularly dangerous in environments where debug logging has been inadvertently left enabled in production, or where logs are aggregated to centralized logging systems like Elasticsearch, Splunk, or cloud-native logging services. The exposed JWT tokens contain authentication claims that could be used to impersonate legitimate users.

The attack requires network access but no authentication or user interaction, making it exploitable remotely by any attacker who can trigger authentication failures and subsequently access the logs through another vulnerability or misconfiguration.

Root Cause

The root cause is improper handling of sensitive authentication data in the logging subsystem. When OIDC authentication fails, the error handling code includes the complete bearer token in the log message without masking or redacting the sensitive portions. The DEBUG log level was likely intended for development troubleshooting but poses significant security risks when enabled in production environments.

Attack Vector

An attacker can exploit this vulnerability through the following attack chain:

1. The attacker sends malformed or invalid OIDC authentication requests to the Oxia service to trigger authentication failures
2. If DEBUG logging is enabled, the full JWT bearer token from these requests is written to application logs
3. The attacker then gains access to logs through a separate vulnerability, misconfigured log aggregation, or insider access
4. Captured JWT tokens can be replayed to authenticate as legitimate users

The vulnerability mechanism centers on the authentication failure handling path. When an OIDC token validation fails, the logging subsystem records the complete request details including the authorization header. This behavior is described in the GitHub Security Advisory.

Detection Methods for CVE-2026-40945

Indicators of Compromise

• Presence of JWT bearer tokens in application log files
• Unusual authentication failures followed by successful authentications from different sources
• Evidence of log file access or exfiltration attempts
• Session tokens being used from unexpected IP addresses or geographic locations

Detection Strategies

• Audit log files and log aggregation systems for exposed JWT tokens using regex patterns matching JWT format
• Monitor for suspicious patterns of authentication failures that could indicate token harvesting attempts
• Implement log analysis rules to detect and alert on bearer token patterns in log entries
• Review access logs for log management systems to identify unauthorized access

Monitoring Recommendations

• Enable alerting for DEBUG log level being enabled in production Oxia deployments
• Monitor for unusual authentication patterns such as rapid authentication failures followed by successes
• Implement log redaction or masking at the log aggregation layer as a defense-in-depth measure
• Track JWT token usage patterns to identify potential token replay attacks

How to Mitigate CVE-2026-40945

Immediate Actions Required

• Upgrade Oxia to version 0.16.2 or later immediately
• Disable DEBUG logging in all production Oxia deployments
• Rotate any JWT tokens or secrets that may have been exposed in logs
• Review and purge historical logs that may contain exposed bearer tokens

Patch Information

The vulnerability is fixed in Oxia version 0.16.2. The patch prevents bearer tokens from being logged in plaintext when OIDC authentication fails. Organizations should upgrade to this version or later as soon as possible. For detailed information about the fix, refer to the GitHub Security Advisory.

Workarounds

• Set log level to INFO or higher in production environments to prevent DEBUG-level token exposure
• Implement log redaction rules at the log aggregation layer to mask JWT patterns
• Restrict access to application logs and log aggregation systems to authorized personnel only
• Consider implementing a reverse proxy or API gateway that sanitizes authentication headers before they reach Oxia

# Configuration example - Ensure DEBUG logging is disabled in production
# Set Oxia log level to INFO or higher
export OXIA_LOG_LEVEL=INFO

# Alternative: Configure via application configuration file
# log:
#   level: info