CVE-2020-9492: Apache Hadoop Auth Bypass Vulnerability

CVE-2020-9492 Overview

CVE-2020-9492 is an authorization bypass vulnerability affecting Apache Hadoop's WebHDFS client. The flaw occurs when the WebHDFS client improperly sends SPNEGO (Simple and Protected GSSAPI Negotiation Mechanism) authorization headers to remote URLs without adequate verification of the destination. This can lead to credential theft and unauthorized access to sensitive resources when a malicious actor can control or redirect WebHDFS requests.

Critical Impact

Authenticated attackers with low privileges can exploit this vulnerability over the network to achieve high impact on confidentiality, integrity, and availability of affected systems. SPNEGO credential leakage can enable lateral movement and unauthorized access across Kerberos-authenticated environments.

Affected Products

• Apache Hadoop versions 3.2.0 to 3.2.1
• Apache Hadoop versions 3.0.0-alpha1 to 3.1.3
• Apache Hadoop versions 2.0.0-alpha to 2.10.0
• Apache Solr versions 8.6.0 and 8.6.2
• Oracle Financial Services Crime and Compliance Management Studio versions 8.0.8.2.0 and 8.0.8.3.0

Discovery Timeline

• 2021-01-26 - CVE-2020-9492 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-9492

Vulnerability Analysis

This vulnerability falls under CWE-863 (Incorrect Authorization), where the WebHDFS client fails to properly validate the destination before transmitting SPNEGO authentication credentials. In Kerberos-authenticated Hadoop environments, the WebHDFS client uses SPNEGO for secure authentication. However, when following HTTP redirects or making requests to external URLs, the client does not adequately verify that the target server is authorized to receive the SPNEGO token.

The practical impact allows an attacker who can influence redirect targets or manipulate network traffic to capture valid Kerberos credentials. These captured credentials can then be replayed to access other services within the Kerberos realm, potentially compromising additional systems and data.

Root Cause

The root cause lies in the WebHDFS client's HTTP request handling logic, which automatically includes SPNEGO authorization headers when making requests without first validating that the target URL belongs to a trusted domain or service. The client treats all destinations equivalently, regardless of whether they are part of the original trusted Hadoop cluster or potentially malicious external endpoints.

This design flaw violates the principle of least privilege, as authentication credentials should only be sent to explicitly trusted destinations. The absence of URL validation before credential transmission creates the authorization bypass condition.

Attack Vector

The attack is network-based and requires low privileges to execute. An attacker can exploit this vulnerability through several methods:

1. Redirect Manipulation: Configuring a malicious redirect on a compromised or attacker-controlled service that the WebHDFS client accesses, causing credentials to be sent to an attacker-controlled server
2. Man-in-the-Middle: Intercepting WebHDFS traffic and injecting redirect responses pointing to credential-harvesting endpoints
3. DNS Poisoning: Redirecting legitimate Hadoop hostnames to attacker infrastructure to capture authentication tokens

The vulnerability does not require user interaction, making it particularly dangerous in automated data processing pipelines where WebHDFS clients operate without human oversight.

Detection Methods for CVE-2020-9492

Indicators of Compromise

• Unusual outbound HTTP/HTTPS connections from Hadoop nodes to external or unexpected IP addresses containing SPNEGO tokens
• Kerberos authentication failures or anomalies following successful WebHDFS operations
• Network traffic showing HTTP redirects from WebHDFS endpoints to non-Hadoop infrastructure
• Unexplained access to resources by service accounts typically associated with WebHDFS clients

Detection Strategies

• Monitor network traffic from Hadoop cluster nodes for WebHDFS requests to external or unauthorized destinations
• Implement SIEM rules to detect SPNEGO/Negotiate authentication headers in requests to non-trusted domains
• Review Kerberos Domain Controller logs for unusual ticket requests or authentication patterns from Hadoop service accounts
• Deploy network segmentation monitoring to alert on Hadoop client communications outside expected network zones

Monitoring Recommendations

• Configure Web Application Firewalls to inspect and log all outbound HTTP Authorization headers containing Negotiate tokens
• Enable verbose logging on WebHDFS clients to capture all redirect events and final destination URLs
• Implement Kerberos audit logging to track service ticket usage and detect potential credential replay attacks
• Use network flow analysis tools to baseline normal WebHDFS communication patterns and alert on deviations

How to Mitigate CVE-2020-9492

Immediate Actions Required

• Upgrade Apache Hadoop to version 3.2.2 or later, 3.1.4 or later, or 2.10.1 or later depending on your version branch
• Review and update Apache Solr installations if using affected versions (8.6.0 or 8.6.2)
• Audit network configurations to restrict outbound connections from Hadoop cluster nodes
• Implement network segmentation to limit WebHDFS client communication to trusted Hadoop services only

Patch Information

Apache has released patches addressing this vulnerability. Organizations should consult the Apache Hadoop General Discussion for official patch guidance. For Oracle products, refer to the Oracle Security Alert July 2022 for specific remediation instructions regarding Financial Services Crime and Compliance Management Studio.

Additional vendor advisories are available from NetApp Security Advisory ntap-20210304-0001 for affected NetApp products.

Workarounds

• Configure network firewalls to block outbound HTTP/HTTPS connections from Hadoop nodes to untrusted destinations
• Implement proxy servers with URL whitelisting for all WebHDFS client traffic
• Use network segmentation to isolate Hadoop clusters and prevent credential leakage to external networks
• Review and harden Kerberos configurations to implement shorter ticket lifetimes, reducing the window for credential replay

# Network restriction example using iptables
# Restrict WebHDFS client outbound connections to trusted Hadoop namenode only
iptables -A OUTPUT -p tcp --dport 9870 -d trusted-namenode.example.com -j ACCEPT
iptables -A OUTPUT -p tcp --dport 9870 -j DROP

# Configure Hadoop to use strict redirect following (if supported by your version)
# Add to core-site.xml
# <property>
#   <name>hadoop.http.cross-origin.allowed-origins</name>
#   <value>https://trusted-cluster.example.com</value>
# </property>