CVE-2020-1983 in libslirp
Summary
by MITRE
A use after free vulnerability in ip_reass() in ip_input.c of libslirp 4.2.0 and prior releases allows crafted packets to cause a denial of service.
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Analysis
by VulDB Data Team • 10/12/2024
The vulnerability identified as CVE-2020-1983 represents a critical use-after-free condition within the libslirp library version 4.2.0 and earlier releases. This flaw exists specifically within the ip_reass() function located in the ip_input.c source file, which is responsible for IP packet reassembly operations. The issue arises when processing crafted network packets that exploit memory management inconsistencies during the reassembly process, creating a scenario where freed memory locations are subsequently accessed or modified by subsequent operations.
This use-after-free vulnerability falls under the Common Weakness Enumeration category CWE-416, which specifically addresses the use of freed memory condition. The flaw manifests when the ip_reass() function handles fragmented IP packets, particularly those containing maliciously constructed headers or payload structures that trigger unexpected behavior in the memory management routines. The vulnerability is particularly concerning because it operates at the network protocol layer, where attackers can leverage it through carefully crafted packet sequences that exploit the reassembly logic without requiring special privileges or authentication.
The operational impact of CVE-2020-1983 extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the environment where libslirp is deployed. When exploited, the vulnerability can cause the affected application to crash or become unresponsive, effectively rendering network services unavailable to legitimate users. This makes it particularly dangerous in network infrastructure applications, virtualization platforms, or network appliances that rely on libslirp for packet processing and network communication. The vulnerability is especially problematic in environments where libslirp is used as a component in QEMU virtualization systems, as it could enable attackers to disrupt virtual machine network operations or potentially escalate privileges through exploitation of the underlying memory corruption.
From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and control communications, as the denial of service aspect can be used to disrupt network services that attackers might be attempting to access or manipulate. The exploitation requires knowledge of network protocol structures and memory management patterns, placing it in the domain of advanced persistent threat actors who can craft specific packet sequences to trigger the memory corruption. Organizations using affected versions of libslirp should consider implementing network segmentation and monitoring to detect anomalous packet patterns that might indicate exploitation attempts. The recommended mitigation involves upgrading to libslirp version 4.2.1 or later, which includes patches specifically addressing the memory management issues in the ip_reass() function. Additionally, network administrators should implement proper input validation and packet filtering rules to reduce the attack surface, though these measures provide only partial protection against this class of vulnerability.