Azure Sphere Unsigned Code Execution Vulnerability

Vulnerability

A vulnerability exists in the signed code execution functionality of Microsoft Azure Sphere version 20.05 that allows an attacker to bypass the platform's memory protection (W^X) policy. The normal world enforces that memory marked writable cannot become executable and vice versa. However, using a specially crafted shellcode that invokes the ptrace system call, an attacker can write to otherwise non-writable memory regions, effectively bypassing this restriction [1].

Exploitation

An attacker must have the ability to execute shellcode on the target Azure Sphere device, typically achieved through a separate compromise or by running a malicious application. The attack requires local access (AV:L) but does not require authentication (PR:N) or user interaction (UI:N). The attacker crafts shellcode that uses ptrace to modify memory that was previously marked non-writable, allowing the injection of executable payloads into protected regions [1].

Impact

Successful exploitation results in unsigned code execution on the Azure Sphere device. The attacker can write arbitrary code into memory regions that should be protected, leading to a high impact on integrity (C:N/I:H/A:N) without affecting confidentiality or availability. This can undermine the trusted execution environment of the device [1].

Mitigation

Microsoft released a fix for this vulnerability as part of an update to Azure Sphere. Users should update to a patched version of the Azure Sphere OS (version 20.06 or later, as referenced in related advisories). No workaround is available for unpatched systems. The vulnerability is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog as of the publication date [1].