CVE-2021-37404: Apache Hadoop Buffer Overflow Vulnerability

CVE-2021-37404 Overview

A critical heap buffer overflow vulnerability exists in Apache Hadoop's libhdfs native code library. The flaw occurs when opening a file path provided by a user without proper validation, potentially allowing attackers to trigger a denial of service condition or achieve arbitrary code execution on affected systems.

Critical Impact

This heap buffer overflow vulnerability in Apache Hadoop's libhdfs native library can be exploited remotely without authentication to cause denial of service or execute arbitrary code on vulnerable big data infrastructure.

Affected Products

• Apache Hadoop versions prior to 2.10.2
• Apache Hadoop versions 3.0.x through 3.2.2
• Apache Hadoop versions 3.3.x prior to 3.3.2

Discovery Timeline

• June 13, 2022 - CVE-2021-37404 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2021-37404

Vulnerability Analysis

CVE-2021-37404 is a heap buffer overflow vulnerability (CWE-787: Out-of-bounds Write) affecting the native libhdfs component of Apache Hadoop. The vulnerability stems from improper handling of user-supplied file paths in the native C library that provides HDFS filesystem access. When a maliciously crafted file path is processed without adequate bounds checking, the native code can write data beyond the allocated heap buffer boundaries.

The libhdfs library serves as a critical interface between applications and the Hadoop Distributed File System (HDFS), making this vulnerability particularly concerning for organizations running big data workloads. Successful exploitation requires network access to the affected Hadoop service but does not require authentication or user interaction, significantly lowering the barrier to attack.

Root Cause

The root cause of this vulnerability is the absence of proper input validation when processing file path strings in the libhdfs native code. When a file path is opened through the native library interface, the code fails to adequately verify the length and content of the path before copying it into a fixed-size heap buffer. This allows an attacker to supply an oversized or specially crafted path that overflows the allocated memory region.

Attack Vector

The attack vector for CVE-2021-37404 is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by sending specially crafted requests containing malicious file paths to a vulnerable Hadoop instance. The attack flow typically involves:

1. Identifying a network-accessible Apache Hadoop deployment running a vulnerable version
2. Crafting a malicious file path designed to overflow the heap buffer in libhdfs
3. Sending the crafted path through an interface that utilizes the native libhdfs library
4. Achieving either denial of service through application crash or potentially arbitrary code execution by controlling the overwritten memory contents

The vulnerability manifests in the libhdfs native code's file path handling routines. When user-supplied file paths are processed without proper length validation, heap memory corruption can occur. For detailed technical analysis, refer to the Apache Mailing List Thread.

Detection Methods for CVE-2021-37404

Indicators of Compromise

• Unexpected crashes or segmentation faults in Hadoop NameNode or DataNode processes with libhdfs in the stack trace
• Abnormally long file path strings in HDFS access logs
• Memory corruption errors or core dumps from native Hadoop components
• Unusual network traffic patterns targeting HDFS file operations

Detection Strategies

• Monitor Hadoop service logs for segmentation faults or heap corruption indicators in native code components
• Implement application-level logging to capture and analyze file path parameters before processing
• Deploy network intrusion detection signatures to identify oversized or malformed file path requests
• Use runtime application self-protection (RASP) tools to detect buffer overflow attempts

Monitoring Recommendations

• Enable verbose logging for libhdfs operations to capture file path handling events
• Set up alerting for process crashes in Hadoop ecosystem components
• Monitor system memory usage patterns for anomalies that may indicate exploitation attempts
• Implement log aggregation and correlation to detect attack patterns across distributed Hadoop clusters

How to Mitigate CVE-2021-37404

Immediate Actions Required

• Upgrade Apache Hadoop to version 2.10.2, 3.2.3, 3.3.2 or higher immediately
• Review network access controls to limit exposure of Hadoop services to trusted networks only
• Audit applications using libhdfs native library for proper input validation
• Implement network segmentation to isolate big data infrastructure from untrusted networks

Patch Information

Apache has released security patches addressing this vulnerability in multiple release branches. Users should upgrade to one of the following fixed versions:

• Apache Hadoop 2.10.2 or later for the 2.x branch
• Apache Hadoop 3.2.3 or later for the 3.2.x branch
• Apache Hadoop 3.3.2 or later for the 3.3.x branch

For additional information, consult the Apache Mailing List Thread and the NetApp Security Advisory.

Workarounds

• Restrict network access to Hadoop services using firewall rules to limit exposure to trusted clients only
• Implement application-level input validation for file paths before passing them to libhdfs functions
• Consider using Java-based HDFS client libraries instead of native libhdfs where feasible
• Deploy web application firewalls (WAF) or API gateways to filter malicious file path inputs

# Example: Restrict Hadoop service access using iptables
# Allow only trusted network to access HDFS NameNode (port 8020)
iptables -A INPUT -p tcp --dport 8020 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8020 -j DROP

# Allow only trusted network to access HDFS DataNode (port 9866)
iptables -A INPUT -p tcp --dport 9866 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9866 -j DROP