Azure Sphere Unsigned Code Execution Vulnerability

Vulnerability

An unsigned code execution vulnerability exists in the normal world's signed code execution functionality of Microsoft Azure Sphere 20.05 [1]. The flaw allows a process to write to its own non-writable memory segments through the /proc/self/mem interface, effectively bypassing the platform's enforcement that memory marked executable cannot be written and vice versa [1]. This circumvents an intended security constraint where mprotect calls that would transition between writable and executable permissions are rejected [1].

Exploitation

An attacker with the ability to execute code on the Azure Sphere device (e.g., through a compromised high-level application) can craft shellcode that writes to /proc/self/mem at runtime [1]. No authentication or user interaction is required beyond local code execution. The attacker can modify pre-existing executable memory regions as the /proc/self/mem write does not undergo the same permission change checks [1].

Impact

Successful exploitation allows the attacker to alter the contents of executable memory pages, leading to arbitrary code execution with the privileges of the compromised process [1]. The integrity impact is high, while confidentiality and availability are not directly affected [1]. The attacker can execute unsigned code not validated by the Azure Sphere's signed code enforcement [1].

Mitigation

Microsoft released a security update as part of Azure Sphere 20.06 and later versions to address this vulnerability [1]. Users should ensure their devices are updated to a patched version. No workaround is available for the vulnerable 20.05 release. This CVE is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog as of November 2020.