page.title= Security updates and resources
@jd:body

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  <div id="qv">
    <h2>In this document</h2>
    <ol id="auto-toc"></ol>
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</div>

<h2 id=android_security_bug_lifecycle>Android security bug lifecycle</h2>

<p>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.</p>

<p>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 <a
href="https://code.google.com/p/android/issues/list">Android Open Source
Project (AOSP) bug tracker</a>, 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.</p>

<h2 id=report-issues>Reporting security issues</h2>

<p>Any developer, Android user, or security researcher can notify the Android
security team of potential security issues through the AOSP bug tracker <a
href="https://code.google.com/p/android/issues/entry?template=Security%20bug%20report">Security
bug report</a> template.</p>

<p>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.</p>

<p>If you need to reach the Android security team for a purpose other than
reporting a vulnerability, please contact <a
href="mailto:security@android.com">security@android.com</a>. The Android
security team has a <a
href="https://developer.android.com/security_at_android_dot_com.txt">PGP
key</a> if you need to encrypt your message.</p>

<h2 id=triaging_bugs>Triaging bugs</h2>

<p>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.</p>

<h3 id=severity>Severity</h3>

<p>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:</p>
<p class="table-caption" id="severity-criteria">
  <strong>Table 1.</strong> Severity ratings and associated consequences</p>
<table>
 <tr>
    <th>Rating</th>
    <th>Consequence of successful exploitation</th>
 </tr>
 <tr>
    <td><strong>Critical</strong></td>
    <td>
<ul>
<li>Remote privileged code execution (execution at a privilege level that
third-party apps cannot obtain)
<li>Local permanent device compromise (device cannot be repaired without
re-flashing the entire operating system, such as a  verified boot or Trusted
Execution Environment/TEE compromise)
<li>Remote permanent denial of service (inoperability, either completely permanent
or requiring re-flashing the device)
</ul>
</td>
 </tr>
 <tr>
    <td><strong>High</strong></td>
    <td>
<ul>
<li>Remote unprivileged code execution (execution at a privilege level that
third-party apps can obtain through installation)
<li>Local access to system/signature-level permission data or capabilities without
permission
<li>Local permanent denial-of-service (inoperability, either completely permanent
or requiring re-flashing the device)
<li>Remote temporary denial-of-service (remote hang or reboot)
</ul>
</td>
 </tr>
 <tr>
    <td><strong>Moderate</strong></td>
    <td>
<ul>
<li>Access to "<a
href="http://developer.android.com/guide/topics/manifest/permission-element.html#plevel">dangerous</a>"
level permission data or capabilities without permission with an app installed
on the device
<li>Local temporary denial-of-service (can be resolved only through a factory
reset)
</ul>
</td>
 </tr>
 <tr>
    <td><strong>Low</strong></td>
    <td>
<ul>
<li>Access to "<a
href="http://developer.android.com/guide/topics/manifest/permission-element.html#plevel">normal</a>"
level permission capabilities without permission with an app installed on the
device
<li>Local temporary denial-of-service (can be resolved by booting the device into
Safe Mode and removing the problem application)
</ul>
</td>
 </tr>
</table>

<p>Though there are many types of software bugs outside of the security
vulnerabilities detailed above, bugs reported are evaluated on a
case-by-base basis to determine what security impact they have.</p>

<p>The Android security team may also adjust the severity of a vulnerability if it
is determined the risk to users is higher or lower than the guidelines suggest.
For example, if a certain piece of data is available only to apps with "system"
level access but the data itself is not sensitive, the Android security
team may consider it only a low-severity vulnerability.</p>

<h4 id=local_vs_remote>Local vs. remote</h4>

<p>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.</p>

<p>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.</p>

<h4 id=high_privilege_levels>Severity of vulnerabilities that affect high privilege levels</h4>

<p>The Android security team will usually drop the severity rating for a bug that
already requires executing code at a high privilege level. For example, a bug
in a kernel driver accessible only from a privileged service that
requires first compromising the service. In this case, the Android security
team may drop the severity from "high" to "moderate."</p>

<h4 id=severity_of_kernel_compromises>Severity of kernel compromises</h4>

<p>Whether a vulnerability that compromises the kernel is considered "high" or
"critical" depends on the device and the version of Android. On devices with a
TEE (or TrustZone) and <a
href="http://source.android.com/devices/tech/security/verifiedboot/index.html">verified
boot</a>, a kernel compromise is considered "high" because exploiting it won't
allow permanently affecting the operation of the device unless a vulnerability is
discovered in the TEE or verified boot implementation. In general, if the
result of a compromise can be remediated with a factory reset, it's "high" or
lower.</p>

<p>However, on older devices without verified boot, a kernel compromise can result
in permanent device compromise if SELinux is disabled and the system partition
is modified. On that device, a kernel compromise is considered "critical"
because remediation requires re-flashing the device's firmware image.</p>

<h3 id=affected_component>Affected component</h3>

<p>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.</p>

<p>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.</p>

<p>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. </p>

<h2 id=notifying_partners>Notifying partners</h2>

<p>When a moderate or higher severity security vulnerability in AOSP is fixed,
we'll notify <a href="http://www.openhandsetalliance.com/">Open Handset
Alliance</a> members with the details of the issue and provide patches for the
most recent three Android releases. The Android security team currently
provides patches for Android versions 4.4 (KitKat), 5.0 (Lollipop), and 5.1
(Lollipop MR1). This list of backport-supported versions changes with each new
Android release.</p>

<h2 id=releasing_code_to_aosp>Releasing code to AOSP</h2>

<p>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.</p>

<h2 id=android_updates>Receiving Android updates</h2>

<p>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 <a
href="https://developers.google.com/android/nexus/images">Nexus factory
images</a> that can be side-loaded to devices.</p>

<h2 id=updating_google_services>Updating Google services</h2>

<p>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
<a href="https://support.google.com/accounts/answer/2812853">Verify Apps</a>
feature to warn users about applications that may be potentially harmful.</p>

<h2 id=other_resources>Other resources</h2>

<p>Information for Android application developers: <a
href="https://developer.android.com">https://developer.android.com</a></p>

<p>The Android security team can be reached at <a
href="mailto:security@android.com">security@android.com</a>. Our PGP key: <a
href="https://developer.android.com/security_at_android_dot_com.txt">https://developer.android.com/security_at_android_dot_com.txt</a></p>

<p>Security information exists throughout the Android Open Source and Developer
sites. Good places to start:<br>
<a href="http://source.android.com/devices/tech/security/index.html">http://source.android.com/devices/tech/security/index.html</a><br>
<a href="https://developer.android.com/guide/topics/security/security.html">https://developer.android.com/guide/topics/security/security.html</a></p>

<p>Security best practices for developers: <a
href="https://developer.android.com/guide/practices/security.html">https://developer.android.com/guide/practices/security.html</a>.</p>

<p>Community resource for discussion about Android security: <a
href="https://groups.google.com/forum/?fromgroups#!forum/android-security-discuss">https://groups.google.com/forum/?fromgroups#!forum/android-security-discuss</a></p>