CVE-2026-76928 in Wireshark
Summary
by MITRE • 08/20/2026
X.509IF protocol dissector crash in 4.6.0 to 4.6.7 and 4.4.0 to 4.4.18 allows denial of service
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Analysis
by VulDB Data Team • 08/20/2026
The X.509IF protocol dissector vulnerability represents a critical stability issue within the specified versions of network packet analysis software, specifically affecting releases from version 4.6.0 through 4.6.7 and 4.4.0 through 4.4.18. This flaw is rooted in improper input validation during the parsing of X.509 Internet Framework messages, which are commonly encountered in secure communication protocols such as TLS or IPsec. When a dissector processes malformed or unexpectedly structured data packets containing specific ASN.1 encoding errors or boundary violations, it fails to handle memory allocation and pointer dereferencing correctly. This technical deficiency leads directly to an application crash, resulting in a denial of service condition for the user running the analysis tool. The vulnerability is primarily classified under CWE-20 Improper Input Validation and CWE-400 Uncontrolled Resource Consumption, as the malformed input triggers unhandled exceptions or memory corruption that terminates the process unexpectedly.
From an operational perspective, this vulnerability poses a significant risk to security professionals and network administrators who rely on packet capture tools for traffic analysis, forensic investigation, and protocol debugging. An attacker with the ability to inject crafted packets into the monitored network segment can exploit this flaw by sending specially constructed X.509IF messages designed to trigger the parsing error. Upon receipt of these malicious packets, the dissector will crash, effectively halting all ongoing packet capture and analysis activities. This disruption not only interrupts real-time monitoring but also compromises the integrity of any captured data streams that were in progress at the time of the crash. In environments where continuous network visibility is critical for threat detection, such as intrusion detection systems or security information and event management platforms utilizing passive sniffing capabilities, this denial of service can create blind spots that adversaries may exploit to conduct further attacks undetected.
The technical mechanism behind this vulnerability typically involves a buffer overflow or an out-of-bounds memory access within the ASN.1 decoder used by the X.509IF dissector. When parsing complex certificate structures or extension fields, if the software does not strictly enforce length constraints or validate tag-value pairs against expected formats, it may attempt to read from invalid memory addresses. This behavior aligns with ATT&CK technique T1498 Network Denial of Service, where an adversary disrupts service availability by exploiting implementation flaws in network protocols. The impact is localized to the application instance processing the traffic rather than affecting underlying infrastructure components directly, but the loss of analytical capability serves as a functional denial of service for security operations teams.
Mitigation strategies primarily involve upgrading the affected software to patched versions where these input validation checks have been rigorously implemented and tested. For organizations unable to immediately patch their analysis workstations or servers due to operational constraints, implementing network-level filtering rules can provide temporary relief by blocking suspicious X.509IF traffic from untrusted sources before it reaches the vulnerable dissector. Additionally, deploying intrusion prevention systems configured with signatures for malformed ASN.1 structures can help filter out malicious packets that attempt to exploit this flaw. It is also advisable to restrict access to packet capture interfaces and analysis tools to authorized personnel only, reducing the attack surface available to potential adversaries seeking to disrupt security monitoring capabilities through resource exhaustion or application crashes.