CVE-2017-1081 in FreeBSD
Summary
by MITRE
In FreeBSD before 11.0-STABLE, 11.0-RELEASE-p10, 10.3-STABLE, and 10.3-RELEASE-p19, ipfilter using "keep state" or "keep frags" options can cause a kernel panic when fed specially crafted packet fragments due to incorrect memory handling.
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Analysis
by VulDB Data Team • 09/21/2020
The vulnerability identified as CVE-2017-1081 affects FreeBSD operating systems across multiple release versions including 11.0-STABLE, 11.0-RELEASE-p10, 10.3-STABLE, and 10.3-RELEASE-p19. This security flaw resides within the ipfilter subsystem which is responsible for packet filtering and stateful inspection capabilities. The vulnerability specifically manifests when ipfilter is configured with either the "keep state" or "keep frags" options, which are commonly used for maintaining connection state information and fragment reassembly respectively. The flaw represents a critical kernel-level issue that can lead to system instability and denial of service conditions.
The technical root cause of this vulnerability stems from improper memory management during packet fragment processing within the ipfilter module. When the system encounters specially crafted packet fragments that trigger the "keep state" or "keep frags" functionality, the kernel fails to properly handle memory allocation and deallocation operations. This incorrect memory handling leads to memory corruption conditions that ultimately result in kernel panics. The vulnerability is particularly dangerous because it occurs at the kernel level where memory corruption can cause immediate system crashes without proper error recovery mechanisms. The flaw demonstrates poor defensive programming practices in memory management and lacks proper bounds checking for fragment processing operations.
The operational impact of CVE-2017-1081 extends beyond simple system crashes to encompass broader network service availability concerns. Systems running affected FreeBSD versions with ipfilter configured using the vulnerable options become susceptible to denial of service attacks where malicious actors can craft specific packet fragments to trigger kernel panics. This vulnerability affects network infrastructure devices, firewalls, and any system relying on ipfilter for packet filtering operations. The attack vector requires minimal privileges as the vulnerability is triggered through normal network packet processing, making it particularly concerning for network security appliances and servers. Organizations utilizing FreeBSD systems for network filtering operations face significant risk of service disruption and potential complete system unavailability.
Mitigation strategies for this vulnerability involve immediate system updates to patched FreeBSD releases that address the memory handling issues in ipfilter. System administrators should prioritize upgrading to FreeBSD 11.0-RELEASE-p11 or 10.3-RELEASE-p20 and later versions where the memory corruption issues have been resolved. In environments where immediate upgrades are not feasible, administrators can disable the vulnerable ipfilter options by removing the "keep state" and "keep frags" parameters from ipfilter rules. Additionally, implementing network monitoring solutions to detect and block suspicious packet fragments can provide temporary protection. The vulnerability aligns with CWE-129, which addresses improper validation of array indices, and reflects ATT&CK technique T1499.002 for network denial of service attacks. Organizations should also consider implementing intrusion detection systems to monitor for potential exploitation attempts and maintain comprehensive backup and recovery procedures for affected systems.