CVE-2017-8065 in Linux
Summary
by MITRE
crypto/ccm.c in the Linux kernel 4.9.x and 4.10.x through 4.10.12 interacts incorrectly with the CONFIG_VMAP_STACK option, which allows local users to cause a denial of service (system crash or memory corruption) or possibly have unspecified other impact by leveraging use of more than one virtual page for a DMA scatterlist.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2017-8065 resides within the Linux kernel's cryptographic subsystem, specifically in the crypto/ccm.c file that implements the Counter with Cipher Block Chaining Message Authentication Code algorithm. This flaw affects kernel versions 4.9.x and 4.10.x through 4.10.12, creating a critical security concern that can be exploited by local attackers to compromise system stability and potentially execute arbitrary code. The vulnerability manifests when the kernel is configured with the CONFIG_VMAP_STACK option enabled, which allows the kernel to use virtual memory mapping for stack allocation. This configuration creates a complex interaction scenario where the cryptographic subsystem fails to properly handle DMA scatterlists that span multiple virtual pages, leading to memory management inconsistencies that can result in system crashes or memory corruption.
The technical root cause of this vulnerability stems from improper handling of memory mappings when the kernel's virtual memory management system interacts with cryptographic operations that require DMA scatterlist processing. When CONFIG_VMAP_STACK is enabled, the kernel allocates stack memory using virtual memory mapping techniques that differ from traditional physical memory allocation. The crypto/ccm.c implementation does not adequately account for this virtual memory structure when processing scatterlists that require multiple virtual pages, creating a scenario where memory references become invalid or corrupted during cryptographic operations. This issue falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions, and represents a classic example of improper memory management in kernel space. The flaw specifically impacts the kernel's ability to correctly manage memory references when processing cryptographic data structures that span virtual memory boundaries, creating potential for both denial of service and potential privilege escalation scenarios.
The operational impact of CVE-2017-8065 extends beyond simple system crashes, as local attackers can leverage this vulnerability to cause unpredictable behavior within the kernel's memory management subsystem. The vulnerability can be triggered through legitimate kernel operations that involve cryptographic processing with DMA scatterlists, making it particularly dangerous in environments where kernel crypto operations are frequently performed. System administrators may observe unexpected kernel oops messages, memory corruption errors, or complete system hangs when this vulnerability is exploited. The memory corruption aspect of this vulnerability aligns with ATT&CK technique T1068, which involves local privilege escalation through kernel vulnerabilities, as attackers could potentially use this flaw to gain elevated privileges. The denial of service component affects system availability and can be particularly problematic in production environments where system uptime is critical, as even a single exploitation attempt could cause significant service disruption.
Mitigation strategies for CVE-2017-8065 focus on both immediate kernel updates and configuration adjustments to prevent exploitation. The most effective remediation involves upgrading to kernel versions that contain the specific fix for this vulnerability, which was implemented in kernel versions 4.10.13 and later. System administrators should also consider disabling the CONFIG_VMAP_STACK option if the system does not require virtual memory stack allocation, as this eliminates the problematic interaction between virtual memory management and cryptographic operations. Additionally, monitoring systems should be configured to detect unusual kernel memory operations or memory corruption patterns that may indicate exploitation attempts. Organizations should implement regular kernel patching procedures and maintain current security baselines to prevent exploitation of similar vulnerabilities. The vulnerability demonstrates the importance of thorough testing of kernel configuration options and their interactions, particularly in cryptographic subsystems where memory management complexities can create unexpected security implications. Network segmentation and privilege separation should also be employed to limit potential damage from successful exploitation attempts, as the vulnerability's impact can extend beyond simple denial of service to include potential privilege escalation scenarios.