CVE-2020-25866 in Wireshark
Summary
by MITRE • 10/06/2020
In Wireshark 3.2.0 to 3.2.6 and 3.0.0 to 3.0.13, the BLIP protocol dissector has a NULL pointer dereference because a buffer was sized for compressed (not uncompressed) messages. This was addressed in epan/dissectors/packet-blip.c by allowing reasonable compression ratios and rejecting ZIP bombs.
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Analysis
by VulDB Data Team • 11/16/2020
The vulnerability identified as CVE-2020-25866 represents a critical NULL pointer dereference flaw within the Wireshark network protocol analyzer software. This issue affects versions 3.2.0 through 3.2.6 and 3.0.0 through 3.0.13, where the BLIP protocol dissector fails to properly handle memory allocation for message buffers. The fundamental problem stems from incorrect buffer sizing that assumes compressed message formats rather than uncompressed data structures, creating a scenario where the software attempts to dereference a null pointer during protocol analysis operations.
The technical implementation flaw occurs within the epan/dissectors/packet-blip.c file where the BLIP protocol dissector processes network traffic. When analyzing BLIP protocol messages, the dissector allocates memory buffers based on assumptions about compression ratios that are not validated against actual message characteristics. This misalignment between expected and actual buffer sizes leads to a situation where the software allocates insufficient memory for uncompressed data, causing subsequent memory access violations when the code attempts to process the received data. The vulnerability operates under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations.
The operational impact of this vulnerability extends beyond simple software crashes, as it represents a potential denial of service condition that could be exploited by malicious actors. Network security analysts and forensic investigators who rely on Wireshark for protocol analysis may experience unexpected application termination when processing specially crafted BLIP protocol traffic. The vulnerability particularly affects environments where automated network monitoring or security analysis systems depend on continuous Wireshark operation, as even a single malicious packet could cause system instability. This flaw aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through application-level exploitation.
The remediation implemented in the patched versions addresses the root cause by enforcing reasonable compression ratio limits and implementing protection against ZIP bomb attacks. This defensive programming approach ensures that buffer allocations are properly validated against actual message characteristics rather than assumptions about compression efficiency. The solution prevents the allocation of insufficient memory buffers while maintaining compatibility with legitimate BLIP protocol traffic patterns. The fix demonstrates proper input validation and resource management practices that align with secure coding standards, effectively closing the memory access violation that previously occurred during protocol analysis operations.
This vulnerability highlights the importance of proper buffer management and input validation in network protocol analysis tools where malformed data could lead to system instability. The issue serves as a reminder that protocol dissectors must account for various data formats and compression scenarios while maintaining robust error handling mechanisms. Security professionals should ensure that network analysis tools are regularly updated to address such vulnerabilities, particularly in environments where automated monitoring systems process untrusted network traffic from multiple sources.