CVE-2025-27821: Apache Hadoop Buffer Overflow Vulnerability

CVE-2025-27821 Overview

CVE-2025-27821 is an Out-of-bounds Write vulnerability affecting the Apache Hadoop HDFS native client. This memory corruption flaw allows attackers to write data beyond the boundaries of allocated memory buffers in the native client component, potentially leading to data corruption, application crashes, or arbitrary code execution.

This vulnerability affects Apache Hadoop versions from 3.2.0 before 3.4.2. Organizations running vulnerable versions are strongly encouraged to upgrade to version 3.4.2, which contains the security fix for this issue.

Critical Impact

An out-of-bounds write vulnerability in the HDFS native client can allow remote attackers to corrupt memory, potentially leading to denial of service or code execution in big data processing environments.

Affected Products

• Apache Hadoop versions 3.2.0 through 3.4.1
• Apache Hadoop HDFS native client component
• Systems using cpe:2.3:a:apache:hadoop:*:*:*:*:*:*:*:*

Discovery Timeline

• 2026-01-26 - CVE CVE-2025-27821 published to NVD
• 2026-01-27 - Last updated in NVD database

Technical Details for CVE-2025-27821

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), a memory corruption vulnerability that occurs when the HDFS native client writes data outside the bounds of an allocated memory buffer. The flaw exists in the native client component of Apache Hadoop HDFS, which is used for high-performance file system operations.

Out-of-bounds write vulnerabilities are particularly dangerous because they can corrupt adjacent memory regions, overwrite critical data structures, or modify control flow data such as return addresses and function pointers. In the context of a distributed file system like HDFS, this could have significant implications for data integrity and system stability across the cluster.

The vulnerability is accessible over the network without requiring authentication or user interaction, making it potentially exploitable in environments where the HDFS native client is exposed to untrusted network traffic.

Root Cause

The root cause of this vulnerability lies in improper boundary checking within the HDFS native client code. When processing certain inputs, the native client fails to properly validate buffer sizes before performing write operations, allowing data to be written past the end of allocated memory regions. This is a common pattern in native code (C/C++) where manual memory management is required.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker could potentially exploit this flaw by sending specially crafted requests to a system running the vulnerable HDFS native client. The vulnerability does not require prior authentication or privileges, and no user interaction is necessary for exploitation.

Successful exploitation could result in:

• Memory corruption leading to service denial
• Potential arbitrary code execution if an attacker can control the overwritten memory contents
• Data integrity issues in HDFS operations

For detailed technical information about the vulnerability mechanism, refer to the Apache Mailing List Discussion and the OpenWall OSS Security Update.

Detection Methods for CVE-2025-27821

Indicators of Compromise

• Unexpected crashes or segmentation faults in Hadoop HDFS native client processes
• Unusual memory consumption patterns in HDFS-related services
• Core dumps or crash reports from the libhdfs native library
• Anomalous network traffic patterns to HDFS endpoints

Detection Strategies

• Implement memory protection mechanisms (ASLR, DEP/NX) to detect and prevent exploitation attempts
• Deploy runtime application self-protection (RASP) solutions that can detect out-of-bounds memory access
• Monitor system logs for HDFS native client crashes or error messages related to memory operations
• Use SentinelOne Singularity to detect anomalous process behavior and memory corruption attempts

Monitoring Recommendations

• Enable verbose logging for HDFS native client operations to capture potential exploitation attempts
• Monitor for unusual process crashes in Hadoop ecosystem components
• Implement network intrusion detection rules to identify suspicious traffic to HDFS services
• Deploy endpoint detection and response (EDR) solutions on nodes running HDFS native clients

How to Mitigate CVE-2025-27821

Immediate Actions Required

• Upgrade Apache Hadoop to version 3.4.2 or later immediately
• Inventory all systems running Apache Hadoop versions 3.2.0 through 3.4.1
• Implement network segmentation to limit exposure of HDFS native client services
• Review and restrict network access to HDFS endpoints to trusted sources only

Patch Information

Apache has released version 3.4.2 which addresses this vulnerability. Users running affected versions (3.2.0 before 3.4.2) should upgrade to the patched version as soon as possible.

For official patch details and upgrade instructions, refer to the Apache Mailing List Discussion.

Workarounds

• If immediate patching is not possible, consider disabling the HDFS native client and using the Java-based client instead, though this may impact performance
• Implement strict network access controls to limit which hosts can communicate with HDFS services
• Deploy web application firewalls (WAF) or network firewalls with deep packet inspection in front of HDFS endpoints
• Enable memory protection features (ASLR, stack canaries) on systems running the native client

# Example: Restricting network access to HDFS services using iptables
# Allow only trusted hosts to access HDFS NameNode (port 9870) and DataNode (port 9864)
iptables -A INPUT -p tcp --dport 9870 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9864 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9870 -j DROP
iptables -A INPUT -p tcp --dport 9864 -j DROP