Last year we published UnZiploc, our research into Huawei’s OTA update implementation. Back then, we have successfully identified logic vulnerabilities in the implementation of the Huawei recovery image that allowed root privilege code execution to be achieved by remote or local attackers. After Huawei fixed the vulnerabilities we have reported, we decided to take a second look at the new and improved recovery mode update process.
This time, we managed to identify a new vulnerability in a proprietary mode called “SD-Update”, which can once again be used to achieve arbitrary code execution in the recovery mode, enabling unauthentic firmware updates, firmware downgrades to a known vulnerable version or other system modifications.
Recently we have disclosed new advisories related to the remote exploitation of Huawei smartphones.
The research that led to these findings was motivated by analyzing new interfaces for remote code execution on a mobile platform. After our work on exploiting Huawei’s Kirin via its baseband interface, we wanted to explore the possibilities of logic bugs as RCE vectors in a modern smartphone chipset, as opposed to memory corruption scenarios that are more common in public research. Logic bugs can be the most powerful because they have the potential to bypass almost all the exploit mitigations that are the typical focus these days, like ASLR, N^X, sandboxing parser code, etc.
Recently we have presented our research on the remote exploitation of Huawei basebands at Black Hat USA 2021. As part of our findings, we have identified several bootloader vulnerabilities in Huawei Kirin chipsets. In addition to that publication, we have also recently disclosed an additional bootrom vulnerability (CVE-2021-22429) in Huawei Kirins.
As it has been publicized, many of these bootloader vulnerabilities were present in bootrom code. As such, it can come as a surprise that Huawei in fact created a mitigation which was published just before Black Hat, in a July OTA update (updates started from June 29th, to be precise).