CVE-2023-34454: Snappy-java Buffer Overflow Vulnerability

CVE-2023-34454 Overview

CVE-2023-34454 is an integer overflow vulnerability in snappy-java, a fast compressor/decompressor library for Java. Due to unchecked multiplications in the compression functions, an integer overflow may occur in versions prior to 1.1.10.1, causing an unrecoverable fatal error that can lead to denial of service conditions.

The vulnerability exists in the compress() function within Snappy.java, which receives arrays of various primitive types (char, double, float, int, long, and short) and compresses them. When processing these arrays, the length is multiplied by a type-specific factor (e.g., 2 for char) without proper bounds checking. This unchecked multiplication can cause an integer overflow, resulting in a negative value being passed to the native maxCompressedLength function.

Critical Impact

This vulnerability allows remote attackers to cause denial of service through application crashes via specially crafted input that triggers integer overflow in the compression routines.

Affected Products

• Xerial snappy-java versions prior to 1.1.10.1

Discovery Timeline

• 2023-06-15 - CVE CVE-2023-34454 published to NVD
• 2024-12-12 - Last updated in NVD database

Technical Details for CVE-2023-34454

Vulnerability Analysis

The vulnerability resides in the compress(char[] input) function in the Snappy.java file. This function receives an array of characters and compresses it by multiplying the input length by 2 (since each char uses 2 bytes) and passing the result to the rawCompress function.

The fundamental issue is that the length is not validated before the multiplication operation. When multiplying by two, an integer overflow can occur if the input array is sufficiently large, causing the result to wrap around and become negative. The rawCompress function then uses this corrupted length value and passes it to the natively compiled maxCompressedLength function to allocate a byte array.

Since maxCompressedLength treats the length as an unsigned integer, it processes the negative value without raising an error and returns what appears to be a valid value. This returned value is then cast to a signed integer by the Java engine. Two failure scenarios can occur:

1. If the result is negative, a java.lang.NegativeArraySizeException exception is raised while attempting to allocate the array buf
2. If the result is positive but incorrect, the buf array is allocated with insufficient size, causing a fatal Access Violation error during compression

The same vulnerability pattern exists in compress functions that handle double, float, int, long, and short arrays, each using different multipliers that can trigger the same overflow condition.

Root Cause

The root cause is improper input validation in the compression functions (CWE-190: Integer Overflow or Wraparound). The code performs arithmetic operations on array length values without checking whether the multiplication result would exceed the maximum value representable by a signed 32-bit integer. When the length is multiplied by the byte size of the data type (2 for char, 4 for int/float, 8 for double/long), values near Integer.MAX_VALUE / multiplier will overflow.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by providing specially crafted input data to an application using snappy-java for compression. The attack can be triggered by:

1. Sending a large array to any compress function that handles primitive types (char, double, float, int, long, short)
2. The array size must be carefully calculated to cause an integer overflow when multiplied by the type's byte size
3. Upon processing, the application will either throw an exception or crash with a fatal Access Violation error

     public static byte[] compress(char[] input)
             throws IOException
     {
-        return rawCompress(input, input.length * 2); // char uses 2 bytes
+        int byteSize = input.length * 2;
+        if (byteSize < input.length) {
+            throw new SnappyError(SnappyErrorCode.TOO_LARGE_INPUT, "input array size is too large: " + input.length);
+        }
+        return rawCompress(input, byteSize); // char uses 2 bytes
     }

     /**

Source: GitHub Snappy.java Commit Details

Detection Methods for CVE-2023-34454

Indicators of Compromise

• Application crashes with java.lang.NegativeArraySizeException in snappy-java compression calls
• Fatal Access Violation errors occurring during Snappy compression operations
• Unusual memory allocation patterns in Java applications using snappy-java
• Service unavailability following receipt of large data payloads intended for compression

Detection Strategies

• Monitor application logs for NegativeArraySizeException or SnappyError exceptions originating from org.xerial.snappy.Snappy class
• Implement dependency scanning to identify snappy-java versions prior to 1.1.10.1 in your software supply chain
• Use Software Composition Analysis (SCA) tools to detect vulnerable library versions in build artifacts and container images
• Monitor JVM crash logs for Access Violation errors associated with native snappy compression calls

Monitoring Recommendations

• Configure application performance monitoring to alert on repeated compression failures or JVM crashes
• Set up dependency vulnerability scanning in CI/CD pipelines to catch vulnerable snappy-java versions before deployment
• Monitor for abnormally large input data being sent to services that utilize snappy-java compression
• Implement logging around compression operations to capture input sizes and detect potential exploitation attempts

How to Mitigate CVE-2023-34454

Immediate Actions Required

• Upgrade snappy-java to version 1.1.10.1 or later immediately
• Audit all applications and services that include snappy-java as a dependency
• Review transitive dependencies in your projects that may include vulnerable snappy-java versions
• Implement input validation to reject excessively large arrays before passing them to compression functions

Patch Information

The vulnerability has been patched in snappy-java version 1.1.10.1. The fix adds overflow checking after the multiplication operation by comparing the result against the original input length. If the calculated byte size is less than the input length (indicating overflow), a SnappyError with TOO_LARGE_INPUT error code is thrown instead of proceeding with potentially corrupted values.

For detailed patch information, refer to the GitHub Security Advisory GHSA-fjpj-2g6w-x25r and the commit d0042551e4a3509a725038eb9b2ad1f683674d94.

Workarounds

• Implement application-level input validation to limit array sizes before compression operations
• For char arrays, ensure input length does not exceed Integer.MAX_VALUE / 2 (approximately 1 billion elements)
• Apply similar bounds checking for other primitive types based on their byte sizes (4 for int/float, 8 for double/long)
• Consider using the byte array compression method which is not affected by this vulnerability

# Maven dependency update to patched version
# Update pom.xml dependency:
# <dependency>
#     <groupId>org.xerial.snappy</groupId>
#     <artifactId>snappy-java</artifactId>
#     <version>1.1.10.1</version>
# </dependency>

# Gradle dependency update:
# implementation 'org.xerial.snappy:snappy-java:1.1.10.1'

# Verify installed version
mvn dependency:tree | grep snappy-java