CVE-2026-6869: 
Wireshark vulnerability analysis and mitigation

CVE-2026-6869 is a denial-of-service vulnerability in Wireshark's WebSocket protocol dissector caused by improperly controlled sequential memory allocation (CWE-1325). It affects Wireshark versions 4.4.0 through 4.4.14 and 4.6.0 through 4.6.4. The vulnerability was published on April 30, 2026, with patches and an official security advisory released the same day. It carries a CVSS v3.1 base score of 5.5 (Medium) (GitHub Advisory, Wireshark Advisory).

The root cause is CWE-1325 (Improperly Controlled Sequential Memory Allocation): the WebSocket dissector performs unbounded decompression when processing zlib-compressed WebSocket frames, failing to cap total memory consumption across all allocated objects. An attacker can craft a malicious packet capture file (e.g., a "zlib bomb") that, when opened in Wireshark or processed by tshark, triggers runaway memory allocation and crashes the application. Exploitation requires local access and user interaction — specifically, a user must open the malicious .pcap file. A proof-of-concept is publicly available on the Wireshark GitLab issue tracker, including a sample websocket_zlib_bomb.pcap file and reproduction command: ASAN_OPTIONS=detect_leaks=0:allocator_may_return_null=0:max_allocation_size_mb=50 tshark -r /poc/websocket_zlib_bomb.pcap -Y websocket (Wireshark GitLab).

Successful exploitation causes Wireshark or tshark to crash, resulting in a denial of service for the affected application instance. There is no impact on confidentiality or integrity — only availability is affected, and the scope is limited to the Wireshark process itself. The vulnerability does not enable lateral movement, code execution, or data exfiltration, making it a low-severity operational disruption for analysts and network engineers relying on Wireshark for packet analysis (GitHub Advisory, Wireshark Advisory).

A proof-of-concept exploit (a crafted websocket_zlib_bomb.pcap file with concrete reproduction steps) is publicly available on the Wireshark GitLab issue tracker (Wireshark GitLab). There is no evidence of in-the-wild exploitation or threat actor attribution at this time. The EPSS score is approximately 0.013% (2nd percentile), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

1. Craft or obtain the malicious pcap: Create or download a websocket_zlib_bomb.pcap file containing WebSocket frames with a deeply nested or excessively large zlib-compressed payload designed to trigger unbounded decompression.
2. Deliver the file to the target: Social-engineer a Wireshark user into opening the malicious .pcap file, or place it in a location where an analyst is likely to open it (e.g., shared network drive, email attachment).
3. Trigger the crash via Wireshark GUI: The victim opens the file in Wireshark, causing the WebSocket dissector to attempt decompression of the payload, exhausting memory and crashing the application.
4. Alternatively, trigger via tshark CLI: Run ASAN_OPTIONS=detect_leaks=0:allocator_may_return_null=0:max_allocation_size_mb=50 tshark -r /poc/websocket_zlib_bomb.pcap -Y websocket to reproduce the crash in a command-line context (Wireshark GitLab).

• File System: Presence of unexpected or externally sourced .pcap files containing WebSocket traffic, particularly with unusually large compressed payloads; files named websocket_zlib_bomb.pcap or similar.
• Process: Wireshark or tshark process terminating unexpectedly or consuming abnormally high memory before crashing when opening a specific capture file.
• Logs: Application crash logs or core dumps associated with the Wireshark process, particularly referencing the WebSocket dissector or zlib decompression routines.

Users should upgrade Wireshark to version 4.4.15 or later (for the 4.4.x branch) or 4.6.5 or later (for the 4.6.x branch), which contain fixes for this vulnerability (Wireshark Advisory, 4.6.5 Release Notes). As a temporary workaround until patching is possible, avoid opening untrusted or externally sourced packet capture files in vulnerable versions of Wireshark. Linux distribution users should apply vendor-provided packages as they become available (e.g., Debian, SUSE, Red Hat updates have been noted in the community).

The vulnerability received standard coverage from security news outlets, including CyberSecurityNews, which covered it alongside other Wireshark vulnerabilities disclosed in the same release cycle (CyberSecurityNews). The Wireshark project promptly published a security advisory and release notes, and announced the fix via their mailing lists (Wireshark Announce). Community reaction has been measured, consistent with the moderate severity and limited exploitation potential of the flaw.