CVE-2022-33879: Apache Tika DOS Vulnerability

CVE-2022-33879 Overview

CVE-2022-33879 is a Regular Expression Denial of Service (ReDoS) vulnerability in Apache Tika's StandardsExtractingContentHandler component. This vulnerability was discovered after the initial fixes for CVE-2022-30126 and CVE-2022-30973 were found to be insufficient, revealing a separate regex pattern vulnerable to catastrophic backtracking in a different regex within the same handler.

Critical Impact

Attackers can craft malicious input that triggers excessive CPU consumption through regex backtracking, causing denial of service conditions in applications using Apache Tika for content extraction.

Affected Products

• Apache Tika versions prior to 1.28.4
• Apache Tika versions prior to 2.4.1

Discovery Timeline

• 2022-06-27 - CVE-2022-33879 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-33879

Vulnerability Analysis

This vulnerability represents a follow-up security issue to CVE-2022-30126 and CVE-2022-30973, demonstrating that the initial remediation efforts were incomplete. The StandardsExtractingContentHandler class in Apache Tika utilizes regular expressions to parse and extract standards references from document content. A previously unidentified regex pattern within this handler contains inefficient quantifiers that are susceptible to catastrophic backtracking when processing specially crafted input strings.

ReDoS vulnerabilities exploit the non-deterministic finite automaton (NFA) implementation used by most regex engines. When an attacker provides input that causes exponential backtracking iterations, the regex engine consumes excessive CPU cycles attempting to find a match, effectively rendering the application unresponsive.

The vulnerability requires local access and user interaction, meaning an attacker must convince a user to process a malicious document through an application utilizing Apache Tika's StandardsExtractingContentHandler. While the impact is limited to availability (denial of service) without affecting confidentiality or integrity, it can still disrupt document processing pipelines and content extraction services.

Root Cause

The root cause is an inefficient regular expression pattern in the StandardsExtractingContentHandler class that fails to account for pathological input cases. The regex contains nested quantifiers or alternation constructs that create exponential matching complexity when processing specific character sequences. This represents a common pattern where regex patterns designed for legitimate content parsing become vulnerable when adversarial input is considered.

Attack Vector

The attack vector requires local access to the system running Apache Tika and user interaction to trigger the vulnerability. An attacker crafts a document containing specially constructed text strings designed to exploit the vulnerable regex pattern. When a user processes this document using an application that invokes Apache Tika's StandardsExtractingContentHandler, the malicious content triggers catastrophic regex backtracking. The regex engine enters an extremely long computation loop, causing CPU exhaustion and application hang or slowdown.

The attack does not require authentication or elevated privileges, but the local access requirement and need for user interaction to process the malicious document significantly limit the attack surface.

Detection Methods for CVE-2022-33879

Indicators of Compromise

• Abnormally high CPU utilization by Java processes running Apache Tika
• Application timeouts or hangs during document processing operations
• Processing queue backups in content extraction pipelines
• Unusual memory consumption patterns alongside CPU spikes

Detection Strategies

• Monitor Java application performance metrics for anomalous CPU spikes during document parsing
• Implement processing timeouts for Tika extraction operations to detect hung processes
• Review application logs for document processing failures or timeout exceptions
• Audit document sources for potentially malicious files targeting content handlers

Monitoring Recommendations

• Deploy application performance monitoring (APM) with alerting on CPU threshold breaches
• Implement resource consumption baselines for Tika processing workloads
• Configure watchdog processes to detect and restart hung document processing services
• Enable verbose logging for StandardsExtractingContentHandler operations in non-production environments

How to Mitigate CVE-2022-33879

Immediate Actions Required

• Upgrade Apache Tika to version 1.28.4 or later for the 1.x branch
• Upgrade Apache Tika to version 2.4.1 or later for the 2.x branch
• Review and audit all applications utilizing Apache Tika for document processing
• Implement processing timeouts as a temporary mitigation if immediate upgrade is not possible

Patch Information

Apache has released fixed versions that address the vulnerable regex pattern in StandardsExtractingContentHandler. The fixes are available in Apache Tika 1.28.4 for the 1.x series and 2.4.1 for the 2.x series. Organizations should update to these versions or later to remediate the vulnerability.

For additional technical details and discussion, refer to the OpenWall OSS Security Discussion, the Apache Mailing List Thread, and the NetApp Security Advisory NTAP-20220812-0004.

Workarounds

• Implement strict processing timeouts for all Tika content extraction operations
• Disable or avoid using StandardsExtractingContentHandler if standards extraction is not required
• Isolate Tika processing in sandboxed containers with resource limits to contain DoS impact
• Pre-screen documents using file size and content heuristics before Tika processing

# Configuration example - Resource limits for containerized Tika deployments
# Docker run with CPU and memory constraints
docker run --cpus="2.0" --memory="2g" --memory-swap="2g" \
  -e TIKA_TIMEOUT=30000 \
  apache/tika:2.4.1