CVE-2024-3203: Blosc C-blosc2 Buffer Overflow Vulnerability

CVE-2024-3203 Overview

A critical heap-based buffer overflow vulnerability has been identified in c-blosc2, a high-performance data compression library. The vulnerability affects the ndlz8_decompress function located in /src/c-blosc2/plugins/codecs/ndlz/ndlz8x8.c. This flaw allows attackers to trigger a heap-based buffer overflow through specially crafted input, potentially leading to remote code execution, denial of service, or information disclosure.

Critical Impact

This heap-based buffer overflow vulnerability can be exploited remotely without authentication, potentially allowing attackers to execute arbitrary code, crash applications, or gain unauthorized access to sensitive data processed by applications using the c-blosc2 library.

Affected Products

• blosc c-blosc2 versions up to 2.13.2

Discovery Timeline

• 2024-04-02 - CVE-2024-3203 published to NVD
• 2025-04-25 - Last updated in NVD database

Technical Details for CVE-2024-3203

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a memory corruption issue that occurs when data is written beyond the bounds of an allocated heap buffer. The flaw exists within the NDLZ8 decompression codec, specifically in the ndlz8_decompress function that handles 8x8 block decompression operations.

When processing malformed or maliciously crafted compressed data, the decompression routine fails to properly validate input boundaries before writing to the output buffer. This allows an attacker to overflow the heap-allocated buffer, potentially corrupting adjacent memory structures. The vulnerability can be triggered remotely when applications process untrusted compressed data using the affected c-blosc2 library.

The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild against unpatched systems.

Root Cause

The root cause of this vulnerability lies in insufficient bounds checking within the ndlz8_decompress function. The NDLZ codec is designed to handle N-dimensional data compression efficiently, but the implementation in versions up to 2.13.2 does not adequately verify that decompressed output will fit within the allocated buffer space. When processing specially crafted input data, the function writes beyond the heap buffer boundaries, resulting in memory corruption.

Attack Vector

The attack can be executed remotely over a network. An attacker can exploit this vulnerability by providing maliciously crafted compressed data to any application that uses c-blosc2 for decompression. This could occur through various attack scenarios including:

• Uploading malicious compressed files to applications that process user-supplied data
• Sending crafted payloads to services that decompress network data using c-blosc2
• Exploiting data processing pipelines that handle untrusted compressed datasets

The vulnerability requires no authentication or user interaction to exploit, as demonstrated by its network attack vector with low complexity requirements.

Detection Methods for CVE-2024-3203

Indicators of Compromise

• Unexpected application crashes or segmentation faults in processes using c-blosc2 library
• Abnormal heap memory allocation patterns or memory corruption warnings from memory sanitizers
• Suspicious compressed data files with malformed NDLZ8 block structures

Detection Strategies

• Deploy application security monitoring to detect anomalous memory access patterns in c-blosc2-dependent applications
• Implement file integrity monitoring for compressed data inputs before decompression processing
• Use memory sanitizers (AddressSanitizer, Valgrind) in development and staging environments to detect buffer overflow attempts
• Monitor system logs for crash dumps related to heap corruption in data processing workflows

Monitoring Recommendations

• Configure logging for all decompression operations processing external or untrusted data
• Implement rate limiting and input validation for applications accepting compressed data uploads
• Deploy runtime application self-protection (RASP) solutions to detect memory corruption attempts
• Monitor for unusual process behavior including unexpected memory allocation failures

How to Mitigate CVE-2024-3203

Immediate Actions Required

• Upgrade c-blosc2 to version 2.14.3 or later immediately
• Audit applications and dependencies that utilize c-blosc2 for decompression functionality
• Restrict or quarantine processing of untrusted compressed data until patches are applied
• Enable heap protection mechanisms (ASLR, heap canaries) where available to reduce exploitation risk

Patch Information

The Blosc development team has addressed this vulnerability in c-blosc2 version 2.14.3. Organizations should upgrade to this version or later to remediate the heap-based buffer overflow. The patch release is available through the GitHub Release v2.14.3.

Additional vulnerability details and tracking information are available through VulDB #259050.

Workarounds

• Implement strict input validation and size limits on compressed data before processing
• Deploy the application in a sandboxed environment with restricted memory access permissions
• Use network segmentation to limit exposure of services that process compressed data with c-blosc2
• Consider temporarily disabling NDLZ codec functionality if not required for application operations

# Verify c-blosc2 version and upgrade
# Check current installed version
pkg-config --modversion blosc2

# Update to patched version (example for pip-based installations)
pip install --upgrade blosc2>=2.14.3

# For source builds, download and compile v2.14.3 or later
git clone https://github.com/Blosc/c-blosc2.git
cd c-blosc2
git checkout v2.14.3
mkdir build && cd build
cmake ..
make && sudo make install