CVE-2026-5657: Wireshark iLBC Codec DoS Vulnerability

CVE-2026-5657 Overview

CVE-2026-5657 is a Double Free vulnerability (CWE-415) affecting Wireshark, the widely-used network protocol analyzer. The vulnerability exists in the iLBC (internet Low Bitrate Codec) dissector, which can crash when processing malformed packets, leading to a denial of service condition. This flaw impacts Wireshark versions 4.6.0 through 4.6.4 and 4.4.0 through 4.4.14.

Critical Impact

Successful exploitation of this vulnerability allows an attacker to cause Wireshark to crash by crafting malicious network capture data containing specially crafted iLBC codec packets, resulting in denial of service for security analysts and network administrators relying on packet analysis.

Affected Products

• Wireshark 4.6.0 to 4.6.4
• Wireshark 4.4.0 to 4.4.14

Discovery Timeline

• 2026-04-30 - CVE-2026-5657 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-5657

Vulnerability Analysis

This vulnerability is classified as a Double Free (CWE-415), a memory corruption issue that occurs when memory is freed twice. In the context of Wireshark's iLBC codec dissector, improper memory management during packet parsing leads to the same memory region being deallocated multiple times.

The iLBC codec is used for encoding/decoding voice communications and is commonly found in VoIP traffic. When Wireshark attempts to dissect malformed iLBC packets, the vulnerability triggers an application crash, terminating the packet capture and analysis session.

The local attack vector requires user interaction—specifically, a victim must open a malicious capture file or apply a live capture filter that processes attacker-controlled traffic containing the malformed iLBC packets. While the vulnerability does not allow for code execution or information disclosure, the availability impact is significant for organizations relying on continuous network monitoring.

Root Cause

The root cause is improper memory management within the iLBC codec dissector. A Double Free condition arises when code paths allow the same memory allocation to be freed more than once. This typically occurs due to:

• Missing or incorrect tracking of memory ownership
• Error handling paths that free memory already released by normal execution flow
• Race conditions in cleanup routines

When the same memory address is passed to free() or equivalent deallocation functions twice, it corrupts the memory allocator's internal data structures, typically causing an immediate crash or potentially exploitable heap corruption.

Attack Vector

The attack vector for CVE-2026-5657 requires local access and user interaction. An attacker can exploit this vulnerability through the following methods:

1. Malicious Capture Files: Crafting a .pcap or .pcapng file containing malformed iLBC codec packets and convincing a user to open it in Wireshark
2. Network-Based Attack: Injecting malicious packets into network traffic being captured by a Wireshark instance with live capture active
3. Shared Capture Repositories: Uploading malicious capture files to shared analysis platforms or repositories

The attack does not grant the attacker any escalated privileges or access to sensitive data; it is limited to causing denial of service by crashing the Wireshark application.

For detailed technical information about this vulnerability, refer to the Wireshark Security Advisory and the GitLab Wireshark Issue.

Detection Methods for CVE-2026-5657

Indicators of Compromise

• Unexpected Wireshark application crashes during packet analysis sessions
• Crash dumps referencing the iLBC dissector or related memory allocation functions
• Core dumps with double-free signatures in heap management routines
• User reports of Wireshark termination when opening specific capture files

Detection Strategies

• Monitor for repeated Wireshark crashes correlating with specific capture file analysis
• Implement file integrity monitoring on capture file directories for unexpected modifications
• Deploy application crash monitoring to track Wireshark process terminations
• Review Wireshark crash logs for references to iLBC codec components

Monitoring Recommendations

• Configure endpoint detection and response (EDR) solutions to alert on Wireshark crash patterns
• Enable application crash reporting to centralize visibility into affected systems
• Monitor network shares and collaboration platforms for potentially malicious capture files
• Track Wireshark version inventory across the organization to identify vulnerable installations

How to Mitigate CVE-2026-5657

Immediate Actions Required

• Update Wireshark to version 4.6.5 or later for the 4.6.x branch
• Update Wireshark to version 4.4.15 or later for the 4.4.x branch
• Avoid opening capture files from untrusted sources until patched
• Disable the iLBC dissector if not required for analysis workflows

Patch Information

Wireshark has released security updates addressing this vulnerability. Organizations should upgrade to the following versions:

• Wireshark 4.6.x branch: Update to version 4.6.5 or later
• Wireshark 4.4.x branch: Update to version 4.4.15 or later

For complete details on the security fix, refer to the official Wireshark Security Advisory wnpa-sec-2026-20.

Workarounds

• Disable the iLBC protocol dissector via Edit → Preferences → Protocols → iLBC if VoIP analysis is not required
• Use capture filters to exclude iLBC traffic before processing: not udp port 5060
• Process untrusted capture files in isolated environments or virtual machines
• Implement strict file handling policies for capture files received from external sources

# Disable iLBC dissector via command line
wireshark -o "ilbc.enabled:FALSE" capture.pcap

# Alternative: Use tshark with dissector disabled
tshark -o "ilbc.enabled:FALSE" -r capture.pcap