Security Updates and Resources

The Android security team is responsible for managing security vulnerabilities discovered in the Android platform and many of the core Android apps bundled with Android devices.

The Android security team finds security vulnerabilities through internal research and also responds to bugs reported by third parties. Sources of external bugs include issues reported through the Android Security Issue template, published and pre-published academic research, upstream open source project maintainers, notifications from our device manufacturer partners, and publicly disclosed issues posted on blogs or social media.

Reporting security issues

Any developer, Android user, or security researcher can notify the Android security team of potential security issues through the security vulnerability reporting form.

Bugs marked as security issues are not externally visible, but they may eventually be made visible after the issue is evaluated or resolved. If you plan to submit a patch or Compatibility Test Suite (CTS) test to resolve a security issue, please attach it to the bug report and wait for a response before uploading the code to AOSP.

Triaging bugs

The first task in handling a security vulnerability is to identify the severity of the bug and which component of Android is affected. The severity determines how the issue is prioritized, and the component determines who fixes the bug, who is notified, and how the fix gets deployed to users.

Process types

This table covers the definitions of process types. The process type can be defined by the type of application or process or the area in which it runs. This table is ordered from least to most privileged.

Process type Type definition
Constrained process A process that runs in a highly limited SELinux domain.
OR
A process that is significantly more limited than a normal application.
Unprivileged process A third-party application or process.
OR
An application or process that runs in the SELinux untrusted_app domain.
Privileged process An application or process with capabilities that are restricted by SELinux untrusted_app domain.
OR
An application or process with important privileges that a third-party application cannot obtain.
Trusted Computing Base (TCB) Functionality that is part of the kernel, runs in the same CPU context as the kernel (such as device drivers), has direct access to kernel memory (such as hardware components on the device), or is one of a handful of user services that is considered kernel equivalent: init, ueventd, and vold.
Trusted Execution Environment (TEE) A component that is designed to be protected from even a hostile kernel.

Severity

The severity of a bug generally reflects the potential harm that could occur if a bug was successfully exploited. Use the following criteria to determine the severity:

Rating Consequence of successful exploitation
Critical
  • Arbitrary code execution in the TEE
  • Remote arbitrary code execution in a privileged process or the TCB
  • Remote permanent denial of service (device inoperability: completely permanent or requiring re-flashing the entire operating system)
  • Remote bypass of user interaction requirements on package installation or equivalent behavior
  • Secure Boot bypass
High
  • Remote arbitrary code execution in an unprivileged process
  • Arbitrary local code execution in a privileged process or the TCB
  • Unauthorized access to data secured by the TEE
  • Remote access to protected data (data normally accessible only to locally installed apps that request permission, or that is limited to a privileged process)
  • Local permanent denial of service (device inoperability: completely permanent or requiring re-flashing the entire operating system)
  • Remote temporary device denial of service (remote hang or reboot)
  • Remote bypass of user interaction requirements (access to functionality that would normally require either user initiation or user permission)
  • Local bypass of user interaction requirements for any developer or security settings modifications
  • A general bypass for operating system protections that isolate application data from other applications
  • A general bypass for operating system protections that isolate users or profiles from one another
  • Cryptographic Vulnerability in Standard TLS that allows for man-in-the-middle attacks
  • Lockscreen bypass
Moderate
  • Remote arbitrary code execution in a constrained process
  • Local arbitrary code execution in an unprivileged process
  • A general bypass for a defense in depth or exploit mitigation technology in a privileged process, the TCB, or the TEE
  • Bypass of restrictions on a constrained process
  • Remote access to unprotected data (data normally accessible to any locally installed app)
  • Local access to protected data (data normally accessible only to locally installed apps that request permission, or that is limited to a privileged process)
  • Local bypass of user interaction requirements (access to functionality that would normally require either user initiation or user permission)
  • Local permanent denial of service (device requires a factory reset)
  • Cryptographic Vulnerability in standard crypto primitives that allows leaking of plaintext (not primitives used in TLS)
  • Bypass of Device Protection/ Factory Reset Protection
  • Bypass of Carrier Restrictions
  • Targeted prevention of access to emergency services
Low
  • Local arbitrary code execution in a constrained process
  • Cryptographic Vulnerability in non-standard usage
  • A general bypass for a user level defense in depth or exploit mitigation technology in an unprivileged process
No Security Impact (NSI)
  • A vulnerability whose impact has been mitigated by one or more rating modifiers or version-specific architecture changes such that the effective severity is below Low, although the underlying code issue may remain

Local vs. remote

A remote attack vector indicates the bug could be exploited without installing an app or without physical access to the device. This includes bugs that could be triggered by browsing to a web page, reading an email, receiving an SMS message, or connecting to a hostile network. For the purpose of our severity ratings, the Android security team also considers "proximal" attack vectors as remote. These include bugs that can be exploited only by an attacker who is physically near the target device, for example a bug that requires sending malformed Wi-Fi or Bluetooth packets.

Local attacks require the victim to install an app. For the purpose of severity ratings, the Android security team also considers physical attack vectors as local. These include bugs that can be exploited only by an attacker who has physical access to the device, for example a bug in a lock screen or one that requires plugging in a USB cable. The Android security team also considers NFC-based attacks as local.

Rating modifiers

While the severity of security vulnerabilities is often easy to identify, ratings may change based on circumstances.

Reason Effect
Requires running as a privileged process to execute the attack -1 Severity
Vulnerability-specific details limit the impact of the issue -1 Severity
Compiler or platform configurations mitigate a vulnerability in the source code Moderate Severity if the underlying vulnerability is Moderate or higher
Requires tamper-evident physical access -2 Severity
If no SELinux domain can conduct the operation under the Google-provided SEPolicy No Security Impact

Note: A CVE may not be issued for issues assessed as Low or NSI.

Affected component

The development team responsible for fixing the bug depends on which component the bug is in. It could be a core component of the Android platform, a kernel driver supplied by an original equipment manufacturer (OEM), or one of the pre-loaded apps on Nexus devices.

Bugs in AOSP code are fixed by the Android engineering team. Low-severity bugs, bugs in certain components, or bugs that are already publicly known may be fixed directly in the publicly available AOSP master branch; otherwise they're fixed in our internal repositories first.

The component is also a factor in how users get updates. A bug in the framework or kernel will require an over-the-air (OTA) firmware update that each OEM will need to push. A bug in an app or library published in Google Play (e.g., Gmail, Google Play Services, WebView in Lollipop and later versions) can be sent to Android users as an update from Google Play.

Notifying partners

When a security vulnerability in AOSP is fixed in an Android Security Bulletin, we'll notify Android partners of issue details and provide patches. The Android security team currently provides patches for Android versions 4.4 (KitKat) and above. This list of backport-supported versions changes with each new Android release.

Releasing code to AOSP

If the security bug is in an AOSP component, the fix will be pushed out to AOSP after the OTA is released to users. Fixes for low-severity issues may be submitted directly to the AOSP master branch before a fix is available.

Receiving Android updates

Updates to the Android system are generally delivered to devices through OTA update packages. These updates may come from the OEM who produced the device or the carrier who provides service to the device. Google Nexus device updates come from the Google Nexus team after going through a carrier technical acceptance (TA) testing procedure. Google also publishes Nexus factory images that can be side-loaded to devices.

Updating Google services

In addition to providing patches for security bugs, the Android security team also review security bugs to determine if there are other ways to protect users. For example, Google Play scans all applications and will remove any application that attempts to exploit a security bug. For applications installed from outside of Google Play, devices with Google Play Services may also use the Verify Apps feature to warn users about applications that may be potentially harmful.

Other resources

Information for Android application developers: https://developer.android.com

Security information exists throughout the Android Open Source and Developer sites. Good places to start:
https://source.android.com/security/index.html
https://developer.android.com/training/articles/security-tips.html

Reports

Sometimes the Android Security team publishes reports or whitepapers. Here are some of the most recent.

Presentations

The Android Security team presents at various conferences and talks. Here are some of their slides: