CVE-2024-4323
📋 TL;DR
A heap-based buffer overflow vulnerability in Fluent Bit's embedded HTTP server allows attackers to corrupt memory by sending specially crafted trace requests. This can lead to denial of service, information disclosure, or remote code execution. Organizations using Fluent Bit versions 2.0.7 through 3.0.3 for log processing are affected.
💻 Affected Systems
- Fluent Bit
📦 What is this software?
Fluent Bit by Treasuredata
Fluent Bit by Treasuredata
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with SYSTEM/root privileges, allowing complete compromise of the Fluent Bit server and potentially lateral movement.
Likely Case
Denial of service causing Fluent Bit to crash, disrupting log collection pipelines and observability.
If Mitigated
Limited impact if HTTP server is disabled or network access is restricted, though memory corruption could still occur from internal sources.
🎯 Exploit Status
Proof-of-concept exploit code is publicly available. The vulnerability requires sending a malformed HTTP trace request to the vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.0.4
Vendor Advisory: https://github.com/fluent/fluent-bit/commit/9311b43a258352797af40749ab31a63c32acfd04
Restart Required: Yes
Instructions:
1. Download Fluent Bit version 3.0.4 or later from the official repository. 2. Stop the Fluent Bit service. 3. Replace the binary with the patched version. 4. Restart the Fluent Bit service.
🔧 Temporary Workarounds
Disable HTTP Server
allDisable the embedded HTTP server if not required for functionality.
Edit Fluent Bit configuration to remove or comment out HTTP input plugin sections
Set [INPUT] type http to false or remove entirely
Network Access Control
linuxRestrict network access to Fluent Bit's HTTP port (default 2020).
iptables -A INPUT -p tcp --dport 2020 -j DROP
firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="TRUSTED_IP" port protocol="tcp" port="2020" accept'
🧯 If You Can't Patch
- Disable the HTTP input plugin entirely in configuration
- Implement strict network segmentation to isolate Fluent Bit instances from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Check Fluent Bit version: fluent-bit --version. If version is between 2.0.7 and 3.0.3 inclusive, the system is vulnerable.Check Version:
fluent-bit --versionVerify Fix Applied:
After patching, verify version is 3.0.4 or later: fluent-bit --version | grep -E '3\.0\.([4-9]|[1-9][0-9])|([4-9]|\d{2,})\.'📡 Detection & Monitoring
Log Indicators:
- Unexpected crashes or restarts of Fluent Bit process
- Memory allocation errors in Fluent Bit logs
- HTTP requests with malformed trace methods
Network Indicators:
- HTTP TRACE requests to port 2020 from unusual sources
- Unusual traffic patterns to Fluent Bit HTTP endpoints
SIEM Query:
source="fluent-bit" AND ("segmentation fault" OR "memory corruption" OR "HTTP TRACE")🔗 References
- https://github.com/fluent/fluent-bit/commit/9311b43a258352797af40749ab31a63c32acfd04
- https://tenable.com/security/research/tra-2024-17
- https://github.com/fluent/fluent-bit/commit/9311b43a258352797af40749ab31a63c32acfd04
- https://tenable.com/security/research/tra-2024-17
- https://www.vicarius.io/vsociety/posts/linguistic-lumberjack-memory-corruption-in-fluent-bit-cve-2024-4323
