In early 2023, security researchers and packet enthusiasts alike were alerted to a denial-of-service (DoS) vulnerability in Wireshark, the world’s most popular network protocol analyzer. Known as CVE-2023-0414, this flaw resides specifically in the way Wireshark’s EAP (Extensible Authentication Protocol) dissector handles certain network packets. Attackers can exploit this bug to crash Wireshark by sending a malicious packet on a live network or by tricking someone into opening a booby-trapped capture file.

This post digs deep into what CVE-2023-0414 is, how the exploit works, demonstrates how it might crash Wireshark, and, most importantly, how you can protect yourself.

Background: Why Wireshark Matters

Wireshark is an open-source tool for capturing, analyzing, and troubleshooting network traffic. It supports hundreds of protocols, including EAP, which is commonly used in wireless and VPN authentication. Because Wireshark is often used interactively for live analysis or post-mortem on capture files, any crashes can disrupt investigations or even become vectors for targeting analysts themselves.

Where’s the Problem?

Wireshark, up to version 4..2, contains a bug in its EAP dissector. A carefully crafted EAP packet can cause the application to crash. This is a textbook denial-of-service: anyone processing network traffic with these malformed packets is vulnerable.

The flaw was introduced in Wireshark 4.. with changes to the EAP dissector, and public fixes appeared in Wireshark 4..3.

According to the Wireshark Security Advisory wnpa-sec-2023-01:

> "The EAP dissector could crash. It was addressed in Wireshark 4..3 and later. Discovered by the Wireshark community."

Impact

This vulnerability is not a remote code execution but a crash (DoS). However, consider these attack vectors:
- Live Network Traffic: An attacker who can inject packets into a network Wireshark is monitoring can remotely crash the analyst’s Wireshark, potentially halting incident response or analysis.
- Malicious Capture Files: An attacker sends a malicious .pcap file via email or upload. When opened in vulnerable Wireshark versions, the application crashes instantly.

Exploit Details

While the exact crash dumps are not public, analysis of the Wireshark source and patch makes it possible to craft a minimally malicious EAP packet that triggers the crash. Here’s how a typical exploitation process looks:

1. Build a Malicious PCAP

You can use tools like Scapy (Python) to craft a malformed EAP packet and save it as a .pcap file.

Python Example: Crafting a Dangerous EAP Packet with Scapy

Here’s a code snippet that builds a malformed EAP packet. (You should only do this in a controlled, virtual environment!)

from scapy.all import *

# Build an Ethernet/802.1X/EAP frame with incorrect EAP length
pkt = Ether(dst="ff:ff:ff:ff:ff:ff")/\
      Dot1X(type=)/\
      EAP(code=2, id=1, type=1, length=3)  # Length mismatch triggers crash

# Save packet to a file
wrpcap("eap_crash.pcap", pkt)

2. Open in Wireshark 4..–4..2

Load the generated eap_crash.pcap file into a vulnerable Wireshark version. The program will crash while dissecting the invalid EAP packet.

What Exactly Happens?

Due to mishandled packet lengths, the dissector tries to read or process memory past the end of the packet buffer, triggering a segmentation fault or access violation. The fix in this diff adds bounds checking around parsing.

Original References

- NVD: CVE-2023-0414
- Wireshark Security Advisory (wnpa-sec-2023-01)
- Wireshark Commit Fix
- Scapy Documentation

Conclusion

CVE-2023-0414 demonstrates how even non-remote code execution bugs–like a denial-of-service in a packet dissector–can disrupt security work. For forensics and blue teams, always keep your tools updated. For red-teamers and bug hunters, this is a classic pattern: input field length mishandling can bring down critical tooling.

Stay sharp–and patch your Wireshark!

*This post is exclusive content by the author for educational purposes. Don’t use these techniques for anything illegal. Stay responsible!*

Timeline

Published on: 01/26/2023 21:18:00 UTC
Last modified on: 02/01/2023 16:22:00 UTC