CVE-2024-4323: Fluent Bit Memory Corruption Vulnerability

CVE-2024-4323 Overview

CVE-2024-4323 is a critical memory corruption vulnerability affecting Fluent Bit, the popular open-source log processor and forwarder used extensively in cloud-native environments. The vulnerability exists in the embedded HTTP server's parsing of trace requests and can result in denial of service conditions, information disclosure, or remote code execution. This flaw affects Fluent Bit versions 2.0.7 through 3.0.3 and poses a significant risk to organizations running vulnerable deployments, particularly those in containerized and Kubernetes environments where Fluent Bit is commonly deployed for centralized logging.

Critical Impact

Remote attackers can exploit this memory corruption flaw via network-accessible HTTP requests to achieve denial of service, leak sensitive information, or potentially execute arbitrary code on affected systems without authentication.

Affected Products

• Fluent Bit versions 2.0.7 through 3.0.3
• Treasuredata Fluent Bit deployments with the embedded HTTP server enabled
• Cloud-native and Kubernetes logging infrastructures using vulnerable Fluent Bit versions

Discovery Timeline

• 2024-05-20 - CVE-2024-4323 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2024-4323

Vulnerability Analysis

This vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write). The flaw resides in Fluent Bit's embedded HTTP server, specifically in the code responsible for parsing trace requests. When processing maliciously crafted HTTP requests, the server fails to properly validate input boundaries, leading to memory corruption conditions.

The vulnerability is particularly concerning because Fluent Bit is widely deployed in cloud-native architectures, Kubernetes clusters, and enterprise logging pipelines. With a proof-of-concept exploit publicly available, the attack surface for organizations running unpatched versions is substantial.

Root Cause

The root cause of CVE-2024-4323 lies in improper bounds checking within the HTTP trace request parsing logic. When the embedded HTTP server receives specially crafted trace requests, the parsing code does not adequately validate the size of input data before writing to memory buffers. This oversight allows an attacker to trigger a heap-based buffer overflow, corrupting adjacent memory regions and potentially gaining control over program execution flow.

Attack Vector

The attack vector for this vulnerability is network-based and requires no authentication or user interaction. An attacker can exploit CVE-2024-4323 by sending malicious HTTP requests to the Fluent Bit embedded HTTP server. The attack targets the trace request parsing functionality, where carefully constructed payloads can trigger the memory corruption condition.

The exploitation chain typically involves:

1. Identifying a network-accessible Fluent Bit instance with the embedded HTTP server enabled
2. Crafting malicious HTTP trace requests designed to overflow the vulnerable buffer
3. Sending the payload to corrupt memory and achieve the desired outcome (DoS, information disclosure, or RCE)

Technical details and proof-of-concept code are available in the CVE-2024-4323 Exploit POC repository. Additional analysis can be found in the Tenable Security Research Report and the Vicarius technical blog post.

Detection Methods for CVE-2024-4323

Indicators of Compromise

• Unusual HTTP requests to the Fluent Bit embedded server on the monitoring/trace API endpoints
• Unexpected Fluent Bit process crashes or service restarts indicating potential exploitation attempts
• Anomalous memory consumption patterns in Fluent Bit processes
• Network traffic containing malformed or oversized trace request payloads targeting Fluent Bit instances

Detection Strategies

• Monitor network traffic for suspicious HTTP requests targeting Fluent Bit's embedded HTTP server endpoints
• Implement application-level logging to capture and analyze incoming trace requests for anomalies
• Deploy intrusion detection signatures to identify exploitation attempts against CVE-2024-4323
• Use SentinelOne's behavioral AI to detect memory corruption exploitation patterns and anomalous process behavior

Monitoring Recommendations

• Enable detailed access logging on Fluent Bit instances to track all incoming HTTP requests
• Configure alerting for Fluent Bit service disruptions or unexpected restarts
• Implement network segmentation monitoring to detect lateral movement following potential exploitation
• Utilize SentinelOne Singularity platform for real-time threat detection and automated response capabilities

How to Mitigate CVE-2024-4323

Immediate Actions Required

• Upgrade Fluent Bit to version 3.0.4 or later immediately to patch the vulnerability
• If immediate patching is not possible, disable or restrict access to the embedded HTTP server
• Implement network-level controls to limit access to Fluent Bit instances from untrusted networks
• Review and audit all Fluent Bit deployments across your infrastructure to identify vulnerable versions

Patch Information

Treasuredata has released a security patch addressing CVE-2024-4323. The fix is available in the official GitHub commit. Organizations should upgrade to Fluent Bit version 3.0.4 or later, which contains the remediation for this memory corruption vulnerability. The patch addresses the improper bounds checking in the HTTP trace request parsing logic.

Workarounds

• Disable the embedded HTTP server if trace functionality is not required in your deployment
• Implement firewall rules to restrict access to Fluent Bit's HTTP server port from untrusted networks
• Use network segmentation to isolate Fluent Bit instances from direct internet exposure
• Deploy a reverse proxy with request validation in front of Fluent Bit instances to filter malicious requests

# Disable HTTP server in Fluent Bit configuration
# Add or modify in fluent-bit.conf
[SERVICE]
    HTTP_Server  Off
    
# If HTTP server is required, restrict to localhost only
[SERVICE]
    HTTP_Server  On
    HTTP_Listen  127.0.0.1
    HTTP_Port    2020