CVE-2020-2800: Oracle JDK Auth Bypass Vulnerability

CVE-2020-2800 Overview

CVE-2020-2800 is a vulnerability in the Java SE and Java SE Embedded products of Oracle Java SE, specifically affecting the Lightweight HTTP Server component. This vulnerability allows an unauthenticated attacker with network access via multiple protocols to compromise affected Java installations. Successful exploitation can result in unauthorized update, insert, or delete access to some accessible data, as well as unauthorized read access to a subset of accessible data.

The vulnerability is notably difficult to exploit, requiring specific conditions to be met. It can only be exploited by supplying data to APIs in the Lightweight HTTP Server component without using Untrusted Java Web Start applications or Untrusted Java applets—for example, through a web service.

Critical Impact

Attackers can gain unauthorized read and write access to data accessible by Java applications using the Lightweight HTTP Server, potentially compromising confidentiality and integrity of enterprise applications and services.

Affected Products

• Oracle JDK 7u251, 8u241, 11.0.6, and 14
• Oracle JRE 7u251, 8u241, 11.0.6, and 14
• Oracle OpenJDK (multiple versions through 14)
• Java SE Embedded 8u241
• NetApp Active IQ Unified Manager, Cloud Backup, E-Series products, OnCommand Insight, SnapManager
• Debian Linux 8.0, 9.0, 10.0
• Fedora 30, 31, 32
• openSUSE Leap 15.1, 15.2
• Canonical Ubuntu Linux 16.04, 18.04, 19.10

Discovery Timeline

• April 15, 2020 - CVE-2020-2800 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-2800

Vulnerability Analysis

This vulnerability resides in the Lightweight HTTP Server component of Oracle Java SE and Java SE Embedded. The Lightweight HTTP Server (com.sun.net.httpserver) is a simple, embeddable HTTP server implementation included in the JDK that allows developers to create HTTP-based services without requiring external application server dependencies.

The security flaw enables an unauthenticated attacker to manipulate data through the HTTP Server APIs. The impact is constrained to partial confidentiality and integrity compromise—attackers can read a subset of accessible data and perform unauthorized modifications (insert, update, delete operations) on some accessible data. There is no availability impact associated with this vulnerability.

The exploitation requires network access and involves supplying crafted data to the Lightweight HTTP Server APIs. Importantly, this is not exploitable through Java Web Start or Java applets, which limits the attack surface to scenarios where the HTTP Server component is actively used by the application.

Root Cause

The vulnerability stems from improper handling of input data within the Lightweight HTTP Server component. When processing HTTP requests and responses, the component fails to adequately validate or sanitize data supplied through its APIs, allowing attackers to potentially bypass security controls and access or modify data beyond their authorized scope.

Attack Vector

The attack vector for CVE-2020-2800 involves network-based exploitation where an attacker sends specially crafted requests to applications utilizing the Lightweight HTTP Server component. The attack does not require authentication, but the high attack complexity indicates that specific conditions must be met for successful exploitation.

An attacker would target Java applications that expose services through the com.sun.net.httpserver package. By supplying malicious input through HTTP requests to these services, the attacker can trigger the vulnerability and gain unauthorized data access. The attack is constrained to scenarios where:

1. The target application uses the Lightweight HTTP Server APIs
2. The attacker has network access to reach the HTTP service
3. The specific vulnerable code path is reachable through the exposed API endpoints

Due to the high complexity required for exploitation and the network-based attack vector, successful attacks require careful crafting of request data to trigger the vulnerability condition.

Detection Methods for CVE-2020-2800

Indicators of Compromise

• Unusual HTTP request patterns targeting Java-based HTTP services with malformed or crafted headers
• Unexpected data access or modification logs in applications using com.sun.net.httpserver
• Network traffic anomalies indicating reconnaissance or exploitation attempts against Java HTTP endpoints
• Log entries showing unauthorized read or write operations following HTTP requests

Detection Strategies

• Monitor network traffic for suspicious requests targeting Java Lightweight HTTP Server endpoints
• Implement application-level logging to track API calls to the com.sun.net.httpserver package
• Deploy intrusion detection signatures for known Java HTTP Server exploitation patterns
• Conduct regular Java version audits across the environment to identify vulnerable installations

Monitoring Recommendations

• Enable verbose logging for Java applications using the HTTP Server component
• Configure network monitoring to alert on anomalous HTTP traffic to Java services
• Implement data access auditing to detect unauthorized read or write operations
• Review application logs for unexpected exceptions or errors in HTTP request processing

How to Mitigate CVE-2020-2800

Immediate Actions Required

• Inventory all systems running affected Java versions (7u251, 8u241, 11.0.6, 14)
• Prioritize patching for systems exposing Java Lightweight HTTP Server services to untrusted networks
• Apply the Oracle Critical Patch Update from April 2020 to all affected installations
• Review network segmentation to limit exposure of vulnerable Java HTTP services

Patch Information

Oracle addressed this vulnerability in the Oracle Critical Patch Update April 2020. Organizations should upgrade to patched Java versions as specified in the advisory. Multiple Linux distributions have also released security updates:

• Debian Security DSA-4662 and DSA-4668
• Ubuntu Security Notice USN-4337-1
• Gentoo GLSA 202006-22
• NetApp Security Advisory NTAP-20200416-0004

Workarounds

• Restrict network access to Java Lightweight HTTP Server endpoints using firewall rules
• Implement additional authentication layers in front of exposed Java HTTP services
• Consider deploying a web application firewall (WAF) to filter malicious requests
• If the Lightweight HTTP Server is not required, disable or remove the component from deployments

# Example: Restrict access to Java HTTP Server port using iptables
iptables -A INPUT -p tcp --dport 8080 -s trusted_network_cidr -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP