CVE-2026-6528: Wireshark TLS Protocol DoS Vulnerability

CVE-2026-6528 Overview

CVE-2026-6528 is an Infinite Loop vulnerability affecting the TLS protocol dissector in Wireshark versions 4.6.0 through 4.6.4. When processing specially crafted TLS traffic, the dissector can enter an infinite loop, causing the application to become unresponsive and resulting in a denial of service condition. This vulnerability is classified under CWE-835 (Loop with Unreachable Exit Condition).

Critical Impact

Attackers can cause Wireshark to hang indefinitely by crafting malicious TLS packets, disrupting network analysis operations and potentially affecting incident response activities.

Affected Products

• Wireshark 4.6.0
• Wireshark 4.6.1
• Wireshark 4.6.2
• Wireshark 4.6.3
• Wireshark 4.6.4

Discovery Timeline

• 2026-04-30 - CVE-2026-6528 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-6528

Vulnerability Analysis

This vulnerability exists within the TLS protocol dissector component of Wireshark. The flaw allows an attacker to trigger a denial of service condition through carefully crafted network traffic. The attack requires local access, meaning an attacker would need to provide a malicious capture file or capture malicious network traffic that Wireshark then attempts to dissect.

The vulnerability is categorized as CWE-835 (Loop with Unreachable Exit Condition), indicating that the TLS dissector contains a loop construct that, under certain input conditions, cannot reach its termination condition. This results in the application consuming CPU resources indefinitely while attempting to process the malformed TLS data.

Root Cause

The root cause is an infinite loop condition within the TLS protocol dissector. When parsing certain malformed or crafted TLS protocol data, the dissector fails to properly validate loop exit conditions, causing it to iterate indefinitely. This type of vulnerability typically occurs when loop control variables are not properly incremented or when boundary checks fail to account for edge cases in protocol parsing.

Attack Vector

The attack requires local access and user interaction. An attacker can exploit this vulnerability by:

1. Crafting a malicious packet capture (PCAP) file containing specially formed TLS protocol data
2. Convincing a user to open the malicious capture file in Wireshark
3. Alternatively, injecting malicious TLS traffic into a network segment being actively captured by Wireshark

When the TLS dissector attempts to parse the malicious data, it enters an infinite loop, causing Wireshark to become unresponsive. The affected system's CPU utilization will spike as the application continuously iterates through the loop, effectively denying service to users attempting to perform network analysis.

The vulnerability mechanism involves malformed TLS record handling in the protocol dissector. For detailed technical information about the specific parsing flaw, refer to the GitLab Wireshark Work Item #21147 and the official security advisory.

Detection Methods for CVE-2026-6528

Indicators of Compromise

• Wireshark process consuming 100% CPU on a single core for extended periods
• Application becoming unresponsive when opening specific capture files or analyzing live traffic
• Presence of unusual or malformed TLS packets in captured network traffic
• System performance degradation during network analysis activities

Detection Strategies

• Monitor system processes for Wireshark instances exhibiting abnormal CPU consumption patterns
• Implement file integrity monitoring on capture files before opening in Wireshark
• Use automated tools to pre-scan PCAP files for known malformed protocol structures
• Enable verbose logging to identify which dissector is consuming resources when Wireshark hangs

Monitoring Recommendations

• Set up alerts for Wireshark processes exceeding normal CPU thresholds for extended durations
• Monitor endpoint systems used for network analysis for unusual resource consumption
• Implement network segmentation to limit exposure of analysis workstations to potentially malicious traffic
• Review capture file sources and establish trusted channels for receiving capture files

How to Mitigate CVE-2026-6528

Immediate Actions Required

• Update Wireshark to the latest patched version beyond 4.6.4
• Avoid opening capture files from untrusted or unknown sources
• Consider temporarily disabling the TLS dissector if immediate patching is not possible
• Implement endpoint protection on systems running vulnerable Wireshark versions

Patch Information

Wireshark has addressed this vulnerability in releases following version 4.6.4. Users should upgrade to the latest stable release to remediate this issue. Detailed patch information is available in the Wireshark Security Advisory WNPA-SEC-2026-33. Additional technical details can be found in GitLab Work Item #21147 and GitLab Work Item #21151.

Workarounds

• Disable the TLS dissector via Analyze > Enabled Protocols menu by unchecking TLS/SSL
• Use command-line option --disable-protocol tls when launching Wireshark
• Process untrusted capture files in an isolated virtual machine environment
• Use alternative tools like tcpdump for initial traffic inspection before opening in Wireshark

# Disable TLS dissector from command line
wireshark --disable-protocol tls capture_file.pcap

# Alternatively, use tshark with TLS dissector disabled
tshark --disable-protocol tls -r capture_file.pcap