CVE-2017-9074 in Linux
Summary
by MITRE
The IPv6 fragmentation implementation in the Linux kernel through 4.11.1 does not consider that the nexthdr field may be associated with an invalid option, which allows local users to cause a denial of service (out-of-bounds read and BUG) or possibly have unspecified other impact via crafted socket and send system calls.
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-9074 represents a critical flaw in the Linux kernel's IPv6 fragmentation handling mechanism that affects versions through 4.11.1. This issue stems from insufficient validation of the nexthdr field within IPv6 packets, creating a condition where the kernel fails to properly verify that the next header field references valid options before processing fragmented packets. The flaw exists in the kernel's network stack implementation where IPv6 fragmentation logic does not adequately sanitize input data, particularly when dealing with malformed or crafted IPv6 packets that contain invalid next header values.
The technical exploitation of this vulnerability occurs when a local attacker crafts specific socket and send system calls that trigger the kernel's IPv6 fragmentation code path. When the kernel attempts to process fragmented IPv6 packets with invalid nexthdr values, it performs out-of-bounds memory reads that can lead to kernel panics and system crashes. This type of vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and CWE-248, which covers exposure of uninitialized variables. The flaw demonstrates a classic buffer overread scenario where the kernel's IPv6 implementation reads memory beyond the intended bounds when processing the next header field in fragmented packets, causing the kernel to execute unexpected code paths that result in system instability.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the execution environment. Local attackers can leverage this flaw to cause system crashes that may be used as part of a broader attack strategy to destabilize target systems or create conditions for privilege escalation. The vulnerability affects systems running Linux kernel versions up to 4.11.1, making it particularly concerning for organizations that have not yet updated their kernel versions. The attack vector requires local access but can be exploited by any user with access to the system, making it a significant concern for multi-user environments and containerized systems where local privilege escalation opportunities may exist.
From an attack framework perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1068, which covers "Local Privilege Escalation" and T1499, which covers "Endpoint Denial of Service" tactics. The vulnerability demonstrates how kernel-level flaws can be exploited to create system instability that may be leveraged for more advanced attacks. Organizations should prioritize patching this vulnerability by updating to kernel versions 4.11.2 or later where the fix has been implemented. The mitigation strategy involves not only applying the kernel update but also implementing network monitoring to detect unusual IPv6 traffic patterns that might indicate exploitation attempts. System administrators should also consider implementing additional security controls such as network segmentation and access controls to limit the potential impact of local privilege escalation attempts that might arise from this vulnerability.