CVE-2026-76928: 
Wireshark vulnerability analysis and mitigation

CVE-2026-76928 is a NULL Pointer Dereference vulnerability in Wireshark's X.509IF protocol dissector that allows unauthenticated remote attackers to crash the application, resulting in a denial of service. It affects Wireshark versions 4.6.0 through 4.6.7 and 4.4.0 through 4.4.18. The vulnerability was published on August 19, 2026, with a patch advisory released the following day. It carries a CVSS v3.1 base score of 7.5 (High) (GitHub Advisory, Wireshark Advisory).

The root cause is a NULL Pointer Dereference (CWE-476) in Wireshark's X.509IF protocol dissector, triggered when processing malformed X.509IF protocol packets. An unauthenticated attacker can exploit this remotely by sending a specially crafted packet that causes the dissector to dereference a NULL pointer, crashing the Wireshark process. No authentication, privileges, or user interaction are required, and attack complexity is low. The vulnerability is tracked upstream in the Wireshark GitLab issue tracker (GitHub Advisory, Wireshark GitLab).

Successful exploitation causes a crash of the Wireshark application, resulting in a denial of service that disrupts packet capture and analysis operations. There is no impact on confidentiality or data integrity — the vulnerability is limited to availability. In environments where Wireshark is used for continuous network monitoring or forensic analysis, exploitation could blind security teams to ongoing network activity (GitHub Advisory, Wireshark Advisory).

As of the time of disclosure, there is no public proof-of-concept exploit and no evidence of in-the-wild exploitation. The EPSS score is 0.0, indicating a very low probability of exploitation in the near term. The vulnerability has not been added to the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (GitHub Advisory).

1. Reconnaissance: Identify network environments where Wireshark (versions 4.6.0–4.6.7 or 4.4.0–4.4.18) is actively capturing traffic on a network segment accessible to the attacker.
2. Craft malformed packet: Construct a malformed X.509IF protocol packet designed to trigger a NULL pointer dereference in Wireshark's X.509IF dissector.
3. Transmit packet: Inject or broadcast the malformed packet onto the network segment being monitored by the target Wireshark instance, so it is captured and processed by the dissector.
4. Trigger crash: The vulnerable dissector dereferences a NULL pointer when parsing the malformed packet, causing the Wireshark process to crash and disrupting any ongoing packet analysis or monitoring (GitHub Advisory, Wireshark Advisory).

• Process: Unexpected termination (crash) of the Wireshark process (wireshark, tshark, or dumpcap) without user-initiated action.
• Logs: Application crash logs or core dump files generated by Wireshark referencing the X.509IF dissector or a NULL pointer dereference error.
• Network: Unusual or malformed X.509IF protocol packets on monitored network segments, particularly those with anomalous structure or truncated fields that deviate from RFC specifications.

Users should update Wireshark to version 4.6.8 or later (for the 4.6.x branch) or 4.4.19 or later (for the 4.4.x branch) to remediate this vulnerability. As an interim workaround, administrators can disable or restrict the X.509IF protocol dissector within Wireshark's preferences, or limit network access to Wireshark instances exposed to untrusted networks. Upgrading to a patched release is the recommended long-term solution (Wireshark Advisory, GitHub Advisory).