CVE-2020-29129 in libslirp
Summary
by MITRE • 11/27/2020
ncsi.c in libslirp through 4.3.1 has a buffer over-read because it tries to read a certain amount of header data even if that exceeds the total packet length.
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Analysis
by VulDB Data Team • 10/25/2024
The vulnerability identified as CVE-2020-29129 resides within the ncsi.c component of libslirp version 4.3.1 and earlier, representing a critical buffer over-read condition that can lead to system instability and potential exploitation. This flaw specifically manifests when the network control and management protocol implementation attempts to process header data without proper validation of available packet length, creating a scenario where memory access occurs beyond the bounds of allocated buffer space. The issue stems from inadequate input validation mechanisms within the network packet processing logic, particularly affecting the handling of NCSI (Network Control and Management Interface) packets that are used for network management functions in virtualized environments.
The technical implementation of this vulnerability involves a classic buffer over-read scenario where the code performs a read operation on a data structure that may extend beyond the actual packet boundaries. When processing incoming network packets, the ncsi.c module calculates a required header size and attempts to read that amount of data regardless of whether sufficient packet data exists. This condition falls under CWE-129, which specifically addresses insufficient checking of the length of input data, and can be categorized under the broader ATT&CK technique T1059.007 for command and scripting interpreter with focus on network protocol manipulation. The flaw occurs during the packet parsing phase where the system assumes a minimum packet size that may not be guaranteed, leading to memory corruption when the read operation extends beyond the actual packet boundaries.
The operational impact of CVE-2020-29129 extends beyond simple memory corruption, potentially enabling denial of service conditions that can disrupt network services within virtualized environments. Since libslirp is commonly used in QEMU and other virtualization platforms for network emulation, this vulnerability could allow attackers to crash virtual machines or cause unpredictable behavior in network management functions. The over-read condition may expose sensitive memory contents to unauthorized parties, particularly when the read operation accesses memory regions that contain confidential information or system state data. Network administrators and security professionals should be particularly concerned about this vulnerability in environments where QEMU-based virtualization is deployed, as it represents a potential vector for service disruption or information disclosure attacks that could affect the integrity of virtualized network infrastructure.
Mitigation strategies for CVE-2020-29129 should prioritize immediate patching of affected libslirp versions to 4.3.2 or later, where the buffer over-read has been addressed through proper input validation and bounds checking. Organizations should implement network monitoring to detect anomalous packet patterns that might indicate exploitation attempts, while also ensuring that virtualization environments are regularly updated to prevent exploitation of this vulnerability. The fix typically involves adding proper length validation checks before any packet header data is read, ensuring that the amount of data requested does not exceed the actual packet length. Security teams should also consider implementing network segmentation and access controls to limit the potential impact of exploitation, while maintaining continuous vulnerability assessment programs to identify similar issues in other network protocol implementations. This vulnerability highlights the importance of robust input validation in network protocol handlers and serves as a reminder of the critical security implications that can arise from seemingly minor buffer handling flaws in network management components.