CVE-2023-20863: VMware Spring Framework DoS Vulnerability

CVE-2023-20863 Overview

In Spring Framework versions prior to 5.2.24, 5.3.27, and 6.0.8, it is possible for a user to provide a specially crafted Spring Expression Language (SpEL) expression that may cause a denial-of-service (DoS) condition. This vulnerability allows authenticated attackers to disrupt application availability through malicious expression parsing.

Critical Impact

Authenticated attackers can exploit this SpEL expression handling flaw to cause denial-of-service conditions, potentially rendering Spring-based applications unavailable.

Affected Products

• VMware Spring Framework versions prior to 5.2.24
• VMware Spring Framework versions prior to 5.3.27
• VMware Spring Framework versions prior to 6.0.8

Discovery Timeline

• April 13, 2023 - CVE-2023-20863 published to NVD
• February 7, 2025 - Last updated in NVD database

Technical Details for CVE-2023-20863

Vulnerability Analysis

This vulnerability resides in the Spring Expression Language (SpEL) parsing component of the Spring Framework. SpEL is a powerful expression language that supports querying and manipulating object graphs at runtime. The flaw involves improper handling of specially crafted SpEL expressions that can lead to resource exhaustion.

The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption) and CWE-917 (Improper Neutralization of Special Elements used in an Expression Language Statement). When an attacker submits a malformed SpEL expression, the parsing mechanism fails to properly limit resource consumption, allowing the expression evaluation to consume excessive CPU or memory resources.

The attack requires low-privilege authentication but no user interaction, making it exploitable by any authenticated user with the ability to submit SpEL expressions. Successful exploitation results in high availability impact, potentially causing complete service disruption.

Root Cause

The root cause stems from insufficient input validation and resource limitation controls within the SpEL expression parser. The framework does not adequately restrict the complexity or depth of expressions that can be evaluated, enabling attackers to craft expressions that trigger algorithmic complexity attacks or recursive processing loops.

Attack Vector

The attack is network-based and requires authenticated access to an application that processes SpEL expressions. Common attack surfaces include:

• Custom Spring applications that evaluate user-supplied SpEL expressions
• Spring Security configurations using SpEL-based access control expressions
• Spring Data repositories with SpEL query parameters
• Any endpoint accepting SpEL expressions for dynamic evaluation

The vulnerability mechanism involves submitting expressions specifically designed to cause excessive resource consumption during parsing or evaluation. These expressions may exploit recursive patterns, deeply nested structures, or complex operations that overwhelm the expression processor.

For detailed technical information, refer to the Spring Security Advisory for CVE-2023-20863.

Detection Methods for CVE-2023-20863

Indicators of Compromise

• Abnormal CPU utilization spikes correlated with SpEL expression processing
• Memory exhaustion events in Spring-based application containers
• Application unresponsiveness following expression evaluation requests
• Error logs indicating expression parsing failures or timeouts

Detection Strategies

• Monitor application performance metrics for sudden resource consumption increases during expression evaluation
• Implement request logging to capture and analyze SpEL expression inputs
• Configure application-level timeouts for expression evaluation operations
• Deploy runtime application self-protection (RASP) solutions to detect malicious expression patterns

Monitoring Recommendations

• Enable detailed logging for SpEL expression evaluation components
• Set up alerts for abnormal response times on endpoints that process dynamic expressions
• Monitor JVM heap and CPU metrics for Spring applications
• Track authentication events followed by resource exhaustion patterns

How to Mitigate CVE-2023-20863

Immediate Actions Required

• Upgrade Spring Framework to version 5.2.24 or later for the 5.2.x branch
• Upgrade Spring Framework to version 5.3.27 or later for the 5.3.x branch
• Upgrade Spring Framework to version 6.0.8 or later for the 6.0.x branch
• Audit applications for endpoints that accept user-supplied SpEL expressions

Patch Information

VMware has released patched versions addressing this vulnerability. Organizations should upgrade to the following minimum versions:

For complete patch details and upgrade guidance, consult the Spring Security Advisory and the NetApp Security Advisory.

Workarounds

• Restrict SpEL expression input to trusted administrative users only
• Implement input validation to limit expression complexity before evaluation
• Configure resource limits and timeouts for expression processing operations
• Consider disabling dynamic SpEL evaluation in user-facing features until patches are applied

# Maven dependency update example for Spring Framework 5.3.x
# Update pom.xml to specify patched version
mvn versions:use-latest-versions -Dincludes=org.springframework:spring-*
mvn dependency:tree | grep spring-core

# Verify upgraded version
mvn dependency:tree -Dincludes=org.springframework:spring-core