CVE-2026-84515 in macOS
Summary
by MITRE • 09/15/2026
An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. Connecting to a malicious SMB server may lead to kernel memory corruption.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability described involves an out-of-bounds write condition within the Server Message Block (SMB) client implementation in Apple's operating systems. This flaw arises from insufficient validation of input data received from remote servers, specifically when processing certain SMB protocol messages. An attacker who controls or can manipulate a malicious SMB server can craft specific network packets that trigger this memory corruption issue. When the affected system processes these malformed requests, it writes data to a memory location outside the bounds of the allocated buffer. This type of error is classified under CWE-787 as an out-of-bounds write vulnerability, which represents one of the most critical classes of software defects due to its potential for arbitrary code execution and privilege escalation.
The operational impact of this vulnerability is severe because it occurs within the kernel space. Kernel memory corruption allows a remote attacker to potentially execute arbitrary code with kernel-level privileges on the affected macOS devices, including versions prior to Golden Gate 27, Sequoia 15.8, and Tahoe 26.7. By exploiting this flaw, an adversary could gain complete control over the system, bypass security mechanisms such as System Integrity Protection (SIP), install malware, or exfiltrate sensitive data. The attack vector is remote, requiring only network connectivity to a malicious SMB server, which significantly lowers the barrier for exploitation compared to local-only vulnerabilities. This aligns with MITRE ATT&CK techniques related to Remote Code Execution and potentially Privilege Escalation via kernel exploits.
Mitigation strategies primarily involve applying the official software updates provided by Apple that address this issue through improved bounds checking in the SMB client code. Administrators should ensure all macOS devices are updated to at least macOS Golden Gate 27, Sequoia 15.8, or Tahoe 26.7 depending on the specific release track. In environments where immediate patching is not feasible, network-level controls such as firewalls can be configured to restrict SMB traffic from untrusted sources. Additionally, disabling unnecessary SMB services if they are not required for business operations reduces the attack surface. Organizations should also monitor their networks for anomalous SMB traffic patterns that might indicate exploitation attempts and ensure endpoint detection and response solutions are updated to recognize indicators of compromise associated with kernel-level memory corruption exploits.