CVE-2023-33202: Bouncy Castle For Java DoS Vulnerability

CVE-2023-33202 Overview

CVE-2023-33202 is a Denial of Service (DoS) vulnerability affecting Bouncy Castle for Java before version 1.73. The vulnerability exists within the org.bouncycastle.openssl.PEMParser class, which is responsible for parsing OpenSSL PEM encoded streams containing X.509 certificates, PKCS8 encoded keys, and PKCS7 objects. When processing a specially crafted file containing malicious ASN.1 data, the PEMParser triggers an OutOfMemoryError, which can be exploited to cause a denial of service condition.

Critical Impact

Applications using vulnerable versions of Bouncy Castle's PEMParser to process untrusted PEM files can be crashed through memory exhaustion attacks, potentially disrupting cryptographic operations and certificate processing services.

Affected Products

• Bouncy Castle for Java versions prior to 1.73
• Bouncy Castle FIPS Java API (BC-FJA) versions 1.0.2.3 and earlier (fixed in 1.0.2.4)

Discovery Timeline

• November 23, 2023 - CVE-2023-33202 published to NVD
• August 18, 2025 - Last updated in NVD database

Technical Details for CVE-2023-33202

Vulnerability Analysis

This vulnerability is classified as CWE-400 (Uncontrolled Resource Consumption), a resource exhaustion vulnerability that allows attackers to consume excessive system memory. The flaw resides in how the PEMParser class handles ASN.1 data structures during the parsing of PEM-encoded cryptographic objects.

When the PEMParser encounters specially crafted ASN.1 data within a PEM file, it fails to properly validate or limit the size of data structures being processed. This allows an attacker to craft malicious input that causes the parser to allocate excessive amounts of memory, ultimately resulting in an OutOfMemoryError that crashes the Java Virtual Machine or severely degrades application performance.

The vulnerability requires local access and user interaction, meaning an attacker must convince a user or application to process a malicious PEM file. However, in automated systems that process certificates or keys from untrusted sources, this could be exploited without direct user interaction.

Root Cause

The root cause of CVE-2023-33202 is insufficient validation of ASN.1 data structure sizes within the PEMParser implementation. The parser does not adequately constrain memory allocation when processing ASN.1-encoded data, allowing crafted input to trigger unbounded memory consumption.

ASN.1 (Abstract Syntax Notation One) is a standard interface description language for defining data structures that can be serialized and deserialized. PEM files use Base64-encoded ASN.1 structures, and the lack of proper bounds checking on these structures enables the memory exhaustion attack.

Attack Vector

The attack vector is local with required user interaction. An attacker exploits this vulnerability by:

1. Crafting a malicious PEM file containing specially constructed ASN.1 data designed to trigger excessive memory allocation
2. Delivering the malicious file to a target system through various means (email attachment, file upload, repository poisoning)
3. Waiting for the victim application to parse the malicious PEM file using the vulnerable PEMParser class
4. The parser attempts to process the crafted ASN.1 structures, allocating memory until an OutOfMemoryError occurs

The vulnerability specifically targets the PEM parsing functionality used for handling X.509 certificates, PKCS8 keys, and PKCS7 objects. Applications that accept and process PEM files from untrusted sources are at highest risk.

For detailed technical information, refer to the GitHub CVE-2023-33202 Wiki maintained by the Bouncy Castle team.

Detection Methods for CVE-2023-33202

Indicators of Compromise

• Unexpected OutOfMemoryError exceptions in Java applications using Bouncy Castle's PEMParser
• Abnormal memory consumption spikes during certificate or key parsing operations
• Application crashes or JVM terminations coinciding with PEM file processing
• Log entries indicating memory allocation failures in cryptographic parsing components

Detection Strategies

• Implement Software Composition Analysis (SCA) scanning to identify Bouncy Castle versions prior to 1.73 or BC-FJA versions prior to 1.0.2.4
• Monitor JVM heap memory metrics during PEM parsing operations for unusual allocation patterns
• Configure application-level logging to capture exceptions in org.bouncycastle.openssl.PEMParser operations
• Deploy runtime application self-protection (RASP) solutions to detect memory exhaustion attempts

Monitoring Recommendations

• Set up alerts for OutOfMemoryError exceptions in production environments using Bouncy Castle
• Implement JVM memory monitoring with thresholds to detect rapid memory growth during file processing
• Review application logs for repeated parsing failures that may indicate exploitation attempts
• Monitor file upload endpoints and certificate processing services for unusual activity patterns

How to Mitigate CVE-2023-33202

Immediate Actions Required

• Upgrade Bouncy Castle for Java to version 1.73 or later immediately
• For FIPS-compliant deployments, upgrade BC-FJA to version 1.0.2.4 or later
• Audit your application dependencies to identify all instances of vulnerable Bouncy Castle versions
• Review systems that process PEM files from untrusted sources and prioritize their patching

Patch Information

The vulnerability has been addressed in:

• Bouncy Castle for Java: Version 1.73 and later
• Bouncy Castle FIPS Java API (BC-FJA): Version 1.0.2.4 and later

Organizations should update their Maven, Gradle, or other build configurations to use the patched versions. For additional guidance, consult the Bouncy Castle Official Site and the NetApp Security Advisory NTAP-20240125-0001.

Workarounds

• Implement input validation to restrict the maximum size of PEM files before passing them to the PEMParser
• Configure JVM memory limits (-Xmx) to prevent a single application from consuming all system memory
• Isolate PEM parsing operations in sandboxed processes with resource constraints
• Avoid processing PEM files from untrusted sources until the patch can be applied

# Example: Update Bouncy Castle dependency in Maven pom.xml
# Replace existing bcpkix-jdk15on dependency with version 1.73+
# <dependency>
#     <groupId>org.bouncycastle</groupId>
#     <artifactId>bcpkix-jdk15on</artifactId>
#     <version>1.73</version>
# </dependency>

# Verify Bouncy Castle version in your application
mvn dependency:tree | grep bouncycastle

# For Gradle projects, update build.gradle
# implementation 'org.bouncycastle:bcpkix-jdk15on:1.73'