CVE-2023-5345 in Linux
Summary
by MITRE • 10/25/2023
A use-after-free vulnerability in the Linux kernel's fs/smb/client component can be exploited to achieve local privilege escalation.
In case of an error in smb3_fs_context_parse_param, ctx->password was freed but the field was not set to NULL which could lead to double free.
We recommend upgrading past commit e6e43b8aa7cd3c3af686caf0c2e11819a886d705.
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Analysis
by VulDB Data Team • 08/27/2024
The vulnerability identified as CVE-2023-5345 represents a critical use-after-free condition within the Linux kernel's Server Message Block version 3 implementation, specifically affecting the fs/smb/client component. This flaw exists in the smb3_fs_context_parse_param function where memory management errors occur during parameter parsing operations. The vulnerability manifests when the ctx->password field undergoes deallocation but fails to be properly nullified, creating a scenario where subsequent operations might attempt to access freed memory locations. This particular implementation issue directly violates fundamental memory safety principles and creates a pathway for malicious actors to exploit the kernel's SMB client functionality. The vulnerability is classified under CWE-416, which specifically addresses the use of freed memory conditions in software systems.
The operational impact of this vulnerability extends beyond simple memory corruption to enable local privilege escalation attacks, making it particularly dangerous in multi-user environments where unprivileged users might attempt to elevate their system privileges. When an attacker successfully triggers this use-after-free condition, they can manipulate the kernel's memory state to execute arbitrary code with elevated privileges. The double free scenario occurs because the freed memory pointer remains accessible and potentially usable by subsequent code paths, allowing for memory corruption that can be leveraged to gain root access. This type of vulnerability aligns with ATT&CK technique T1068 which focuses on exploiting local privilege escalation opportunities through kernel vulnerabilities. The attack vector requires local system access and can be particularly insidious because it operates within the kernel space where normal user-space protections are ineffective.
The specific technical flaw occurs within the smb3_fs_context_parse_param function where the ctx->password field is freed but not set to NULL, creating a dangling pointer condition. This memory management error allows for a potential double free scenario where the same memory location might be freed twice or accessed after deallocation. The vulnerability is particularly concerning because it operates in a kernel module context where memory corruption can lead to complete system compromise. The recommended fix involves upgrading past commit e6e43b8aa7cd3c3af686caf0c2e11819a886d705 which implements proper nullification of the freed password field. This fix addresses the root cause by ensuring that after memory deallocation, the pointer is explicitly set to NULL to prevent subsequent access attempts. Organizations should prioritize patching this vulnerability as it represents a direct pathway for privilege escalation attacks that could compromise entire systems. The fix demonstrates proper memory management practices that align with secure coding guidelines and kernel security best practices, particularly focusing on preventing dangling pointer conditions that are common in kernel-level memory management errors.