CVE-2020-7039 in libslirp
Summary
by MITRE
tcp_emu in tcp_subr.c in libslirp 4.1.0, as used in QEMU 4.2.0, mismanages memory, as demonstrated by IRC DCC commands in EMU_IRC. This can cause a heap-based buffer overflow or other out-of-bounds access which can lead to a DoS or potential execute arbitrary code.
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Analysis
by VulDB Data Team • 10/15/2024
The vulnerability identified as CVE-2020-7039 resides within the tcp_emu functionality of libslirp version 4.1.0, a critical component utilized by QEMU 4.2.0 for network emulation purposes. This flaw manifests in the tcp_subr.c source file where memory management operations fail to properly validate input data, creating a dangerous condition that can be exploited through IRC DCC commands processed by the EMU_IRC module. The issue represents a fundamental breakdown in input sanitization and memory boundary checking that affects the core networking emulation capabilities of virtualized environments.
The technical implementation of this vulnerability stems from improper handling of buffer operations within the tcp_emu subsystem, specifically when processing IRC DCC (Direct Client-to-Client) commands. When these commands are processed through the EMU_IRC module, the memory allocation and data copying mechanisms fail to account for potential buffer overflows, allowing attackers to craft malicious IRC DCC payloads that exceed allocated buffer boundaries. This mismanagement creates heap-based buffer overflow conditions that can result in memory corruption, leading to unpredictable behavior and system instability. The vulnerability operates at the intersection of network protocol handling and memory management, making it particularly dangerous in virtualized environments where QEMU's network emulation is heavily utilized.
The operational impact of CVE-2020-7039 extends beyond simple denial-of-service conditions to potentially enable arbitrary code execution within the context of the QEMU process. When exploited, the heap-based buffer overflow can be leveraged to overwrite critical memory structures, potentially allowing attackers to redirect execution flow or inject malicious code into the virtual machine environment. This vulnerability is particularly concerning for cloud environments and virtualization platforms where multiple guest operating systems share the same host resources, as successful exploitation could compromise the entire virtualization infrastructure. The attack surface is broadened by the fact that QEMU is widely deployed across various virtualization platforms, making this vulnerability a significant concern for system administrators and security professionals managing virtualized environments.
Mitigation strategies for CVE-2020-7039 should prioritize immediate patching of affected QEMU versions to incorporate fixes for the memory management issues in libslirp 4.1.0. Organizations should implement network segmentation and access controls to limit exposure to IRC DCC commands within virtualized environments, particularly in scenarios where QEMU is used for guest network access. The vulnerability aligns with CWE-121, heap-based buffer overflow, and can be mapped to ATT&CK technique T1059.007 for execution through command and scripting interpreters. Additional defensive measures include implementing network monitoring to detect unusual IRC DCC traffic patterns and deploying intrusion detection systems that can identify potential exploitation attempts. System administrators should also consider isolating virtual machines that process untrusted network traffic and regularly audit QEMU configurations to ensure that unnecessary network emulation features are disabled, reducing the attack surface for this and similar vulnerabilities.