The OnePlus 2 Primary Bootloader (PBL) does not validate the SBL1 partition before executing it, although it contains a certificate. This allows attackers with write access to that partition to disable signature validation.

An issue was discovered on OnePlus One, X, 2, 3, and 3T devices. OxygenOS and HydrogenOS are vulnerable to downgrade attacks. This is due to a lenient 'updater-script' in OTAs that does not check that the current version is lower than or equal to the given image's. Downgrades can occur even on locked bootloaders and without triggering a factory reset, allowing for exploitation of now-patched vulnerabilities with access to user data. This vulnerability can be exploited by a Man-in-the-Middle (MiTM) attacker targeting the update process. This is possible because the update transaction does not occur over TLS (CVE-2016-10370). In addition, a physical attacker can reboot the phone into recovery, and then use 'adb sideload' to push the OTA (on OnePlus 3/3T 'Secure Start-up' must be off).

An issue was discovered on OnePlus One, X, 2, 3, and 3T devices. Due to a lenient updater-script in the OnePlus OTA images, and the fact that both ROMs use the same OTA verification keys, attackers can install HydrogenOS over OxygenOS and vice versa, even on locked bootloaders, which allows for exploitation of vulnerabilities patched on one image but not on the other, in addition to expansion of the attack surface. This vulnerability can be exploited by Man-in-the-Middle (MiTM) attackers targeting the update process. This is possible because the update transaction does not occur over TLS (CVE-2016-10370). In addition, physical attackers can reboot the phone into recovery, and then use 'adb sideload' to push the OTA (on OnePlus 3/3T 'Secure Start-up' must be off).

An issue was discovered in OnePlus One, X, 2, 3, 3T, and 5 devices with OxygenOS 5.0 and earlier. The attacker can reboot the device into the Qualcomm Emergency Download (EDL) mode through ADB or by using Volume-Up when connected to USB, which in turn could allow for downgrading partitions such as the Android Bootloader.