Wireshark is a must-have tool for anyone dealing with network packets, whether you’re troubleshooting issues, doing security research, or reverse engineering protocols. But sometimes the intricate code needed to handle hundreds of network protocols exposes fresh risks.

In 2023, a dangerous bug in Wireshark’s Kafka protocol dissector was discovered, tracked as CVE-2023-3648. A specially crafted Kafka packet or pcap file could instantly crash Wireshark 4..–4..6 and 3.6.–3.6.14, making all packet analysis impossible. This is a classic denial-of-service (DoS) scenario that researchers and blue teams need to know about.

Understanding CVE-2023-3648: The Kafka Dissector Crash

Wireshark uses "dissectors"—chunks of code that know how to decode and display packets for specific network protocols. Kafka, a popular messaging system, got protocol support in Wireshark so teams could debug traffic and spot issues.

But in versions 4..–4..6 and 3.6.–3.6.14, the Kafka dissector had a bug. If Wireshark examined a malformed Kafka packet (in live traffic or a capture file), it could make Wireshark crash immediately. For a busy engineer or SOC analyst, that means losing visibility just when it matters most.

Official bug:
- Wireshark advisory: wnpa-sec-2023-20
- NVD entry: CVE-2023-3648

Who’s affected?

Wireshark 3.6. to 3.6.14

Anyone using these versions on Windows, Linux, or macOS is at risk.

The vulnerability sits in how Wireshark’s Kafka dissector reads Kafka packets. If a user

- Opens a pcap/ng file containing a hand-crafted (malicious) Kafka packet

Monitors live network traffic with a packet matching the bug trigger

Wireshark’s process will try to parse the packet, hit the bug in the dissector code, and crash.

Why is this dangerous?

- It can be exploited remotely using a crafted Kafka packet injected into the network (if you’re analyzing live traffic).
- It can be triggered from a simple file transfer (e.g., receiving a malicious pcap file in an email or download).

Triggering the Bug: A Simple Exploit Example

Let's see what this kind of exploit might look like. Crafting a trigger packet manually would require low-level byte editing, but using tools like Scapy (Python) or editing a pcap with hex editors can do the trick.

Here’s a (hypothetical) Python snippet that crafts a malformed Kafka packet to crash affected Wireshark versions:

# pip install scapy
from scapy.all import *

# Kafka's default port is 9092
ip = IP(dst="10...2")
tcp = TCP(sport=54321, dport=9092, flags="PA")

# Malformed Kafka payload, causing the crash
malicious_kafka_payload = b"\x00" * 100 + b"<trigger bytes>"

pkt = ip / tcp / Raw(malicious_kafka_payload)

# Save to pcap
wrpcap("malicious_kafka.pcap", [pkt])

Open this malicious_kafka.pcap file in a vulnerable version of Wireshark and—boom!—the application will crash.

*(Note: The precise “trigger bytes” depend on the internal bug—in public advisories, the full trigger isn’t shown, to give users time to patch.)*

What Was the Actual Coding Flaw?

According to the official commit, the issue was due to improper bounds or length checking in the Kafka dissector code. The crash typically resulted from stack overflows, buffer overruns, or access violations when untrusted packet data was parsed as Kafka protocol fields.

Patch: Update to Wireshark 4..7 or 3.6.15 (or later).

- Patch commit: Fix crash in Kafka dissector

Takeaways and Lessons

1. Protocol dissectors are risky. They have to parse untrusted data, so bugs can have big consequences.
2. Always check for updates, especially for security tools. Even tools you trust can have critical flaws.

Be careful with pcap files. Treat captures from unknown sources as potentially dangerous.

4. Report bugs responsibly. This issue was fixed swiftly because the community shared it with the Wireshark team.

References & Further Reading

- Wireshark Official Security Advisory: wnpa-sec-2023-20
- NIST NVD – CVE-2023-3648
- Fix commit in Wireshark's Kafka dissector
- Wireshark Download


Stay vigilant, patch often, and respect the power—and the dangers—of packet dissectors. Happy analyzing!

Timeline

Published on: 07/14/2023 07:15:00 UTC
Last modified on: 07/25/2023 18:24:00 UTC