CVE-2018-19333 in gVisor
Summary
by MITRE
pkg/sentry/kernel/shm/shm.go in Google gVisor before 2018-11-01 allows attackers to overwrite memory locations in processes running as root (but not escape the sandbox) via vectors involving IPC_RMID shmctl calls, because reference counting is mishandled.
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Analysis
by VulDB Data Team • 06/11/2023
The vulnerability identified as CVE-2018-19333 resides within the Google gVisor containerization project's kernel implementation, specifically in the shared memory management component located at pkg/sentry/kernel/shm/shm.go. This flaw represents a critical security issue affecting gVisor versions prior to the 2018-11-01 release, where attackers can exploit improper reference counting mechanisms during IPC_RMID shmctl system calls to perform memory overwrites. The vulnerability operates within the confines of the sandboxed environment but presents significant risks to systems running with elevated privileges.
The technical flaw stems from a fundamental error in the reference counting implementation for shared memory segments within gVisor's kernel emulation layer. When IPC_RMID system calls are executed, the system fails to properly maintain reference counts for shared memory objects, leading to premature deallocation of memory regions. This improper handling creates a window where malicious actors can manipulate shared memory structures and overwrite arbitrary memory locations accessible to processes running with root privileges. The vulnerability does not allow sandbox escape but enables privilege escalation within the confined environment through memory corruption techniques. This issue aligns with CWE-129, which addresses improper handling of reference counting mechanisms, and represents a classic case of use-after-free vulnerability within kernel space emulation.
The operational impact of this vulnerability extends beyond simple memory corruption, as it enables attackers to manipulate critical system processes and potentially escalate privileges within the sandboxed environment. Processes running with root privileges become vulnerable to memory overwrites that could compromise system integrity, leading to potential data breaches, privilege escalation, or system instability. The attack vector specifically targets shared memory management operations, making it particularly dangerous in environments where multiple processes share memory segments or where sensitive operations depend on shared memory communication patterns. This vulnerability affects containerized applications that rely on gVisor's kernel emulation for security isolation, potentially undermining the security benefits that containerization is designed to provide.
Mitigation strategies for CVE-2018-19333 primarily involve upgrading to gVisor versions released after November 1, 2018, which contain the necessary fixes for proper reference counting implementation. Organizations should also implement monitoring for suspicious shared memory operations and consider additional security measures such as runtime application control, memory protection mechanisms, and regular vulnerability assessments of containerized environments. The fix addresses the core reference counting issue by ensuring proper cleanup procedures during IPC_RMID operations and maintaining accurate accounting of shared memory segment references. Security teams should also review their container security policies to ensure that root privileges are not unnecessarily granted to containerized applications, as this vulnerability specifically targets scenarios where processes operate with elevated privileges within the sandboxed environment. This vulnerability demonstrates the importance of proper memory management in kernel emulation systems and highlights the need for rigorous testing of reference counting mechanisms in virtualized security environments.