CVE-2026-76926 Overview
CVE-2026-76926 is a denial-of-service vulnerability affecting the BUSMASTER file parser in Wireshark. The flaw allows an attacker to trigger an abnormal exit of the application when a crafted BUSMASTER capture file is opened or processed. Affected versions include Wireshark 4.6.0 through 4.6.7 and 4.4.0 through 4.4.18. The vulnerability is tracked under CWE-617: Reachable Assertion and requires user interaction to be triggered. Exploitation results in loss of availability for the Wireshark process only; confidentiality and integrity are not affected.
Critical Impact
A crafted BUSMASTER capture file causes Wireshark to exit abnormally, disrupting packet capture and analysis workflows for network engineers and incident responders.
Affected Products
- Wireshark 4.6.0 through 4.6.7
- Wireshark 4.4.0 through 4.4.18
- BUSMASTER file parser component within Wireshark
Discovery Timeline
- 2026-08-19 - CVE-2026-76926 published to NVD
- 2026-08-20 - Last updated in NVD database
Technical Details for CVE-2026-76926
Vulnerability Analysis
The vulnerability resides in the BUSMASTER file parser shipped with Wireshark. BUSMASTER is an open-source CAN bus analysis tool, and Wireshark supports parsing its capture log format. When the parser processes a malformed or crafted BUSMASTER file, it reaches an unexpected state that triggers an abnormal exit. The parser fails to validate input conditions gracefully, causing the entire Wireshark process to terminate rather than reject the malformed file.
The impact is limited to availability of the analysis session. An analyst who opens a hostile capture file loses the current session and any unsaved state. There is no memory corruption, arbitrary code execution, or information disclosure associated with this issue.
Root Cause
The root cause is a reachable assertion or unhandled error condition [CWE-617] inside the BUSMASTER file parsing logic. The parser assumes certain structural invariants that a crafted file can violate, and rather than returning a parse error to the caller, the process aborts.
Attack Vector
Exploitation requires an attacker to deliver a crafted BUSMASTER file and convince a user to open it in a vulnerable Wireshark version. Delivery can occur through email attachments, shared file locations, or capture exchanges between engineering teams. The attack complexity is elevated because the input must be shaped precisely to reach the faulty parser path, and successful exploitation only crashes the application.
See the Wireshark Security Advisory wnpa-sec-2026-70 and the GitLab Work Item for upstream technical details.
Detection Methods for CVE-2026-76926
Indicators of Compromise
- Unexpected Wireshark process termination immediately after opening a .log BUSMASTER capture file.
- Application crash events referencing the BUSMASTER dissector or file parser in operating system crash logs.
- Receipt of BUSMASTER capture files from untrusted or unverified sources.
Detection Strategies
- Inventory endpoints running Wireshark versions in the 4.6.0–4.6.7 and 4.4.0–4.4.18 ranges using software asset management tooling.
- Alert on repeated Wireshark process crashes on the same host, which may indicate targeted delivery of malformed capture files.
- Correlate email and file-sharing telemetry for BUSMASTER-formatted attachments delivered to analyst workstations.
Monitoring Recommendations
- Monitor application crash telemetry from analyst and engineering workstations for Wireshark exit codes.
- Track file-open events in Wireshark against known-trusted capture repositories.
- Review endpoint logs for unexpected termination of wireshark.exe or tshark processes across the fleet.
How to Mitigate CVE-2026-76926
Immediate Actions Required
- Upgrade Wireshark to a fixed release above 4.6.7 or 4.4.18 as published in wnpa-sec-2026-70.
- Instruct analysts to open BUSMASTER capture files only when the source is verified.
- Isolate handling of untrusted capture files to non-production analysis workstations.
Patch Information
Wireshark has published a security advisory and fix under wnpa-sec-2026-70. Apply the upstream patched release for the 4.6.x or 4.4.x branch corresponding to your deployment. Details of the code change are tracked in the GitLab Work Item 21435.
Workarounds
- Disable or avoid using the BUSMASTER file parser until the patched Wireshark version is deployed.
- Do not open BUSMASTER capture files received from untrusted sources or unknown senders.
- Use tshark in a sandboxed environment when triage of a suspect BUSMASTER file is required.
# Verify the installed Wireshark version and confirm it is patched
wireshark --version | head -n 1
tshark --version | head -n 1
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
