CVE-2021-22191: Wireshark RCE Vulnerability

CVE-2021-22191 Overview

CVE-2021-22191 is an improper URL handling vulnerability in Wireshark that could allow remote code execution. The vulnerability exists in Wireshark versions 3.4.0 to 3.4.3 and 3.2.0 to 3.2.11, where improper validation of URLs can be exploited via packet injection or by crafting a malicious capture file. When a user opens a specially crafted capture file or processes malicious network traffic, an attacker could potentially execute arbitrary code on the target system.

Critical Impact

Remote code execution through improper URL handling enables attackers to compromise systems running vulnerable Wireshark versions via malicious capture files or injected packets.

Affected Products

• Wireshark 3.4.0 to 3.4.3
• Wireshark 3.2.0 to 3.2.11
• Oracle ZFS Storage Appliance 8.8
• Debian Linux 9.0

Discovery Timeline

• 2021-03-15 - CVE-2021-22191 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-22191

Vulnerability Analysis

This vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly referred to as an injection vulnerability. The core issue lies in how Wireshark processes URLs embedded within network capture data.

When Wireshark encounters URLs in captured packet data or within PCAP files, the application fails to properly validate and sanitize these URL strings before processing them. This improper handling creates an injection vector that attackers can exploit to execute arbitrary code on the system running Wireshark. The vulnerability requires user interaction, meaning a victim must either open a maliciously crafted capture file or capture traffic containing the malicious payload.

Root Cause

The root cause of CVE-2021-22191 is inadequate input validation in Wireshark's URL handling routines. The application does not properly neutralize special elements within URLs before they are processed by downstream components. This allows specially crafted URL strings to escape the intended data context and be interpreted as executable commands or code by the underlying system. The vulnerability represents a classic injection flaw where untrusted input is not properly sanitized before being passed to an interpreter or execution context.

Attack Vector

The attack can be executed through two primary vectors:

1. Malicious Capture File: An attacker creates a specially crafted PCAP or PCAPNG file containing packets with malicious URL data. When a victim opens this file in Wireshark for analysis, the improper URL handling triggers code execution.

2. Packet Injection: In scenarios where an attacker has network access, they can inject packets containing malicious URL payloads into traffic being captured by Wireshark. As the vulnerable Wireshark instance processes the injected packets, the malicious URL is handled improperly, leading to code execution.

Both vectors require some level of user interaction, making this a targeted attack scenario where social engineering or network positioning is typically required.

The vulnerability manifests in how Wireshark processes embedded URLs during packet dissection. For technical details, see the Wireshark Security Notice and the Wireshark Issue Tracker.

Detection Methods for CVE-2021-22191

Indicators of Compromise

• Unusual or unexpected Wireshark process behavior, including spawning child processes
• Detection of capture files with anomalous URL patterns or embedded executable content
• Network traffic showing packet injection attempts targeting Wireshark capture sessions
• System logs indicating command execution originating from Wireshark processes

Detection Strategies

• Monitor for abnormal process creation chains where wireshark.exe or tshark spawns unexpected child processes
• Implement file integrity monitoring on systems where capture files are analyzed
• Deploy network intrusion detection rules to identify malformed packets targeting Wireshark protocol dissectors
• Use behavioral analysis to detect code execution attempts from within Wireshark

Monitoring Recommendations

• Enable verbose logging for Wireshark analysis workstations and review for anomalies
• Implement application whitelisting to prevent unauthorized process execution from Wireshark
• Monitor network shares and file repositories where capture files are stored for suspicious uploads
• Utilize EDR solutions to track process behavior and memory access patterns on analysis systems

How to Mitigate CVE-2021-22191

Immediate Actions Required

• Update Wireshark to version 3.4.4 or later (for 3.4.x series) or 3.2.12 or later (for 3.2.x series)
• Avoid opening untrusted capture files until patches are applied
• Disable or restrict network capture on systems running vulnerable Wireshark versions
• Implement network segmentation to isolate packet analysis workstations

Patch Information

Wireshark has released security updates to address this vulnerability. Users should upgrade to the following versions:

• Wireshark 3.4.x: Upgrade to version 3.4.4 or later
• Wireshark 3.2.x: Upgrade to version 3.2.12 or later

Additional patches are available for downstream distributions:

• Oracle has addressed this in their April 2021 Critical Patch Update for ZFS Storage Appliance
• Debian has released updates via the Debian LTS announcement
• Gentoo users can reference the GLSA Advisory 202107-21

For complete details, review the official Wireshark Security Notice.

Workarounds

• Analyze capture files on isolated virtual machines or sandboxed environments until patches are applied
• Use command-line tools like tshark with limited output options to reduce exposure to URL handling routines
• Implement strict access controls to limit who can provide capture files for analysis
• Consider using alternative network analysis tools temporarily until vulnerable systems are updated

# Check current Wireshark version
wireshark --version

# On Debian/Ubuntu systems, update to patched version
sudo apt update && sudo apt install wireshark

# On RHEL/CentOS systems
sudo yum update wireshark

# Verify installed version is patched (should be >= 3.4.4 or >= 3.2.12)
wireshark --version | grep -E "Wireshark [0-9]+\.[0-9]+\.[0-9]+"