CVE-2024-20926: Oracle GraalVM Auth Bypass Vulnerability

CVE-2024-20926 Overview

CVE-2024-20926 is a confidentiality flaw in the Scripting component of Oracle Java SE, Oracle GraalVM for JDK, and Oracle GraalVM Enterprise Edition. An unauthenticated remote attacker can abuse APIs in the Scripting component to gain unauthorized access to data accessible by the Java runtime. The flaw is exploitable over multiple network protocols and applies to clients running sandboxed Java Web Start applications or sandboxed Java applets that execute untrusted code. Oracle published the issue in the January 2024 Critical Patch Update. The weakness is classified under [CWE-284] (Improper Access Control).

Critical Impact

Successful exploitation allows complete read access to all data accessible to the affected Java SE or GraalVM runtime, including sandboxed deployments that load untrusted code.

Affected Products

• Oracle Java SE: 8u391, 8u391-perf, 11.0.21, 17.0.9, 21.0.1
• Oracle GraalVM for JDK: 17.0.9, 21.0.1; Oracle GraalVM Enterprise Edition: 20.3.12, 21.3.8, 22.3.4
• NetApp Cloud Insights Acquisition Unit, Cloud Insights Storage Workload Security Agent, OnCommand Insight; Debian Linux 10

Discovery Timeline

• 2024-01-16 - Oracle releases the January 2024 Critical Patch Update addressing CVE-2024-20926
• 2024-01-16 - CVE-2024-20926 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-20926

Vulnerability Analysis

The vulnerability resides in the Scripting component shared by Oracle Java SE and Oracle GraalVM. The component exposes APIs that can be reached by untrusted code or via web services that forward attacker-controlled input to the scripting engine. An attacker who reaches these APIs can read data that should be isolated by the Java security model. The impact is limited to confidentiality, but the exposed data may include credentials, configuration material, or other information processed by the runtime. Exploitation has high attack complexity, which reflects the specific conditions required to manipulate the scripting interfaces successfully.

Root Cause

The defect is an improper access control issue [CWE-284] in the Scripting subsystem. The component fails to enforce expected isolation boundaries when invoked by untrusted code or external callers. Sandboxed Java Web Start applications and applets that rely on the Java sandbox to contain untrusted scripts are therefore not protected.

Attack Vector

An unauthenticated attacker reaches the vulnerable APIs over the network. Two scenarios apply: a server that exposes a web service forwarding data into the Scripting APIs, and a client running sandboxed Java code that loads attacker-controlled content from the internet. In both cases the attacker does not need credentials or user interaction beyond loading the malicious payload.

No public proof-of-concept has been released. Refer to the Oracle January 2024 Security Alert for vendor-supplied technical context.

Detection Methods for CVE-2024-20926

Indicators of Compromise

• Unexpected outbound connections from Java processes (java, javaw) to untrusted hosts after loading remote applets or Web Start applications.
• Anomalous invocation of javax.script.ScriptEngineManager or Nashorn/GraalJS scripting interfaces from web-facing services.
• Presence of vulnerable runtime versions such as JDK 8u391, 11.0.21, 17.0.9, or GraalVM 20.3.12, 21.3.8, 22.3.4 on production hosts.

Detection Strategies

• Inventory all Java and GraalVM installations using software asset management or endpoint telemetry and flag installations matching the affected versions.
• Inspect application logs for requests that feed user-controlled data into scripting endpoints, particularly web services exposing JSR-223 engines.
• Correlate process execution events with file reads of sensitive paths originating from java processes to surface scripting-driven data access.

Monitoring Recommendations

• Forward Java application and JVM telemetry to a centralized analytics platform and alert on new uses of scripting APIs in services that should not require them.
• Monitor NetApp OnCommand Insight and Cloud Insights agents for the patched build levels documented in NetApp Security Advisory NTAP-20240201-0002.
• Track package state on Debian hosts using the Debian LTS Announcement to confirm OpenJDK updates are applied.

How to Mitigate CVE-2024-20926

Immediate Actions Required

• Apply the January 2024 Critical Patch Update for Oracle Java SE and GraalVM to all affected systems.
• Update Debian OpenJDK packages and NetApp products according to the vendor advisories.
• Disable Java Web Start and applet support on endpoints that do not require legacy sandboxed Java execution.
• Restrict network exposure of services that feed untrusted input into JSR-223 scripting engines.

Patch Information

Oracle delivered fixes in the Oracle January 2024 Security Alert. Recommended upgrade targets include Oracle JDK 8u401, 11.0.22, 17.0.10, 21.0.2, and GraalVM releases superseding 20.3.12, 21.3.8, and 22.3.4. NetApp documents fixed builds in NTAP-20240201-0002 and NTAP-20241108-0002. Debian distributes patched OpenJDK packages through its LTS channel.

Workarounds

• Remove or disable the Nashorn or GraalJS scripting engines in deployments that do not require server-side scripting.
• Apply a custom Java Security Manager policy that denies ScriptEngine instantiation for untrusted code paths where legacy applets must remain supported.
• Place affected services behind authenticated gateways and validate that user input cannot reach scripting APIs.

# Verify the installed Java version on Linux hosts
java -version 2>&1 | head -n1

# Debian: apply OpenJDK security updates
sudo apt-get update && sudo apt-get install --only-upgrade openjdk-11-jre-headless

# Disable Java Web Start system-wide (example, RHEL/CentOS)
sudo alternatives --remove javaws /usr/bin/javaws || true