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The vulnerability in Elasticsearch Packetbeat stems from improper resource management during IPv4 fragment reassembly. Packetbeat, a network packet analyzer, processes incoming IPv4 fragments to reconstruct original packets. Attackers craft malicious IPv4 fragments designed to trigger excessive resource allocation. These fragments exploit the lack of limits or throttling in Packetbeat’s reassembly logic. When integrated, each fragment causes uncontrolled memory allocation for storage and CPU cycles for processing. The attack is remote and unauthenticated, requiring no prior system access. By sending a stream of crafted fragments, attackers overwhelm Packetbeat’s buffer. This leads to continuous allocation without bounds, exhausting available resources. Memory leakage and high CPU usage degrade performance rapidly. Ultimately, Packetbeat becomes unresponsive, causing denial-of-service. The vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling. It aligns with CAPEC-130: Excessive Allocation attack pattern. Packetbeat’s role in monitoring network traffic makes it susceptible to such injections. The flaw resides in the packet reassembly module handling IPv4 fragmentation. Without checks, fragmented packets consume resources until system failure. This affects availability and stability of the Elastic Stack monitoring capability. Mitigation requires implementing limits on fragment processing and resource controls.
Platform: Elasticsearch Packetbeat
Version: Not specified
Vulnerability: Excessive resource allocation
Severity: High
Date: December 18 2025
Prediction: Patch expected shortly
What Undercode Say:
Analytics
- Use `hping3 –frag` to generate fragmented IPv4 packets.
- Script with Scapy: `send(IP(dst=”target”, flags=”MF”)/TCP())`
– Monitor Packetbeat logs: `tail -f /var/log/packetbeat/packetbeat`
– Check resource usage: `top -p $(pgrep packetbeat)`
– Test with `nmap -f` for fragmentation scans.
How Exploit
- Craft malicious IPv4 fragments with overlapping offsets.
- Flood Packetbeat with fragmented packets using network tools.
- Exploit reassembly logic to cause infinite allocation loops.
Protection from this CVE
- Update Packetbeat to patched version.
- Implement network ingress filtering.
- Limit fragment processing rates.
Impact
- Denial-of-service via resource exhaustion.
- System instability and crashes.
- Reduced monitoring capability.
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Sources:
Reported By: github.com
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