CVE-2026-76929 in Wireshark
Summary
by MITRE • 08/20/2026
Pcapng file parser 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 vulnerability identified involves a critical flaw within the pcapng file parsing logic found in specific versions of network traffic analysis software, specifically affecting releases from version 4.6.0 through 4.6.7 and version 4.4.0 up to 4.4.18. This issue manifests as an application crash when processing malformed or specially crafted pcapng files, leading directly to a denial of service condition for users relying on the software for network monitoring, forensic analysis, or security auditing tasks. The root cause typically stems from improper validation of input data structures during the parsing phase, where the parser fails to adequately check bounds, lengths, or structural integrity before attempting memory allocation or pointer dereferencing operations. This lack of robust error handling allows an attacker who can supply a malicious pcapng file to trigger undefined behavior within the application process space, resulting in immediate termination of the service and potential loss of unsaved work or disruption of ongoing network surveillance activities.
From a technical perspective, this vulnerability aligns with common memory safety issues often categorized under CWE-125 Out-of-bounds Read or CWE-400 Uncontrolled Resource Consumption depending on the specific mechanism triggering the crash. In many cases involving pcapng parsers, the issue arises because the parser does not verify that the file size matches expected header structures or that block lengths are consistent with available data before proceeding to parse nested blocks. When a crafted packet capture file contains truncated headers, invalid length fields, or malformed option records, the internal state machine of the parser may attempt to access memory regions outside its allocated buffer or perform arithmetic operations on corrupted values. This leads to segmentation faults or other fatal exceptions that cause the application to exit unexpectedly. Such flaws are particularly dangerous in environments where pcapng files are ingested from untrusted sources, such as public repositories, email attachments, or network taps managed by third parties, without prior sanitization or validation checks.
The operational impact of this vulnerability is significant for organizations deploying these versions of the software in production environments. A successful exploitation does not require authentication if the application automatically processes incoming files or allows users to open arbitrary pcapng documents through a graphical interface. For command-line tools used in automated pipelines, an attacker could inject malicious capture data into log aggregation systems or intrusion detection pre-processing stages, causing continuous service restarts and rendering security monitoring capabilities ineffective during critical incidents. Furthermore, repeated crashes can lead to resource exhaustion if the application is configured to auto-restart without proper cleanup of temporary files or memory leaks associated with failed parse attempts. This effectively creates a persistent denial-of-service vector that degrades system availability and reliability over time, impacting both operational continuity and incident response capabilities.
Mitigation strategies must focus on immediate version upgrades and defensive coding practices for future development. Users should upgrade to patched versions beyond 4.6.7 and 4.4.18 where the parsing logic has been hardened with strict input validation, bounds checking, and graceful error handling that prevents crashes upon encountering malformed data. In environments where upgrading is not immediately feasible, deploying network-level filters or file inspection gateways can help block suspicious pcapng files before they reach the vulnerable application layer. Additionally, implementing sandboxing techniques such as running the parser in a restricted container environment with limited memory access and no persistent storage can contain the impact of any successful exploitation attempt. Security teams should also enforce strict input validation policies for all external data sources feeding into network analysis tools to ensure that only well-formed packet captures are processed by the engine.
This vulnerability is mapped within industry frameworks such as MITRE ATT&CK under techniques related to resource hijacking or service disruption, specifically reflecting behaviors associated with Denial of Service attacks via application layer exploitation. The lack of proper input validation places it squarely in categories like CWE-20 Improper Input Validation and CWE-787 Out-of-bounds Write if the crash results from buffer overflow conditions rather than simple null pointer dereferences or arithmetic overflows. Understanding these classifications helps security architects prioritize remediation efforts based on risk severity and potential attack vectors. By addressing this flaw, organizations not only restore service stability but also strengthen their overall defense-in-depth posture against file-based application layer attacks that target common data interchange formats like pcapng used extensively in cybersecurity workflows.