CVE-2026-76928: X.509IF Protocol Dissector DoS Vulnerability

CVE-2026-76928 Overview

CVE-2026-76928 is a denial-of-service vulnerability in the Wireshark X.509IF protocol dissector. The flaw affects Wireshark versions 4.6.0 through 4.6.7 and 4.4.0 through 4.4.18. A remote attacker can crash the dissector by supplying a malformed packet capture or by injecting crafted traffic on a monitored network segment. The underlying weakness is a NULL pointer dereference [CWE-476], which terminates the analyzer process and interrupts packet analysis workflows.

Critical Impact
Remote attackers can crash Wireshark without authentication or user interaction, disrupting network monitoring and incident response operations.

Affected Products

Wireshark 4.6.0 through 4.6.7
Wireshark 4.4.0 through 4.4.18
Deployments using the X.509IF dissector for certificate analysis

Discovery Timeline

2026-08-19 - CVE-2026-76928 published to NVD
2026-08-20 - Last updated in NVD database

Technical Details for CVE-2026-76928

Vulnerability Analysis

The defect resides in the X.509IF (Information Framework) protocol dissector, which parses directory-style attributes commonly embedded in X.509 certificate extensions. When the dissector receives a specifically malformed field, control flow reaches a code path that dereferences a pointer without first validating that it references an allocated structure. The result is an immediate process crash.

Because Wireshark is often used to capture live traffic, an attacker sitting on the same broadcast domain as an analyst can transmit a single crafted frame and terminate the capture session. The same outcome occurs when an analyst opens an attacker-supplied .pcap or .pcapng file that contains the malformed X.509IF structure.

Root Cause

The root cause is an unchecked pointer usage inside the X.509IF dissector, classified under [CWE-476] NULL Pointer Dereference. The parser assumes that a sub-structure required for further decoding is present in every input. Malformed encodings violate that assumption and trigger the crash. See the Wireshark Security Advisory WNPA-SEC-2026-87 and GitLab Work Item #21469 for the upstream analysis.

Attack Vector

Exploitation requires no authentication and no user interaction beyond opening a capture file or running a live capture. Two realistic delivery paths exist: injecting crafted packets on a network segment where Wireshark is capturing, and distributing a malicious capture file to an analyst. Both paths result in the analyzer process terminating.

No public exploit code has been published. The vulnerability description confirms the impact is limited to availability; confidentiality and integrity of the host are not affected.

Detection Methods for CVE-2026-76928

Indicators of Compromise

Unexpected Wireshark, tshark, or dumpcap process crashes during live capture or file analysis
Crash dumps referencing the X.509IF dissector or related ASN.1 decoding routines
Repeated malformed frames containing X.509 certificate structures on monitored segments

Detection Strategies

Alert on abnormal termination of analyst workstations' capture tooling, especially when correlated with recent file opens or network taps
Inspect suspicious .pcap and .pcapng files in an isolated environment before analysts open them on production hosts
Track process exit codes and core dumps from wireshark and tshark binaries across the analyst fleet

Monitoring Recommendations

Enforce endpoint monitoring on analyst workstations to record process crashes and parent-child execution chains
Log receipt of capture files from external sources and require validation before opening
Review installed Wireshark versions across the fleet and flag hosts still on vulnerable 4.4.x or 4.6.x builds

How to Mitigate CVE-2026-76928

Immediate Actions Required

Upgrade Wireshark to a fixed release outside the 4.6.0–4.6.7 and 4.4.0–4.4.18 ranges as identified in WNPA-SEC-2026-87
Inventory analyst systems and CI pipelines that invoke tshark or dumpcap and prioritize those exposed to untrusted traffic or files
Restrict the sources of capture files opened by analysts to trusted, internally generated artifacts

Patch Information

The Wireshark Foundation has published fixes referenced in WNPA-SEC-2026-87 and tracked in GitLab Work Item #21469. Administrators should install the latest 4.4.x and 4.6.x maintenance releases from the official Wireshark download channels or their distribution's package repository.

Workarounds

Disable the X.509IF dissector in Wireshark via Analyze > Enabled Protocols until patched builds are deployed
Perform capture analysis inside dedicated, sandboxed virtual machines that can be reverted after each session
Use command-line tools with a minimal dissector set when triaging capture files from untrusted origins

bash

# Disable the X.509IF dissector for tshark sessions
tshark --disable-protocol x509if -r suspicious.pcapng