Vulnerabilities > CVE-2017-5217 - Improper Input Validation vulnerability in Samsung Mobile
Summary
Installing a zero-permission Android application on certain Samsung Android devices with KK(4.4), L(5.0/5.1), and M(6.0) software can continually crash the system_server process in the Android OS. The zero-permission app will create an active install session for a separate app that it has embedded within it. The active install session of the embedded app is performed using the android.content.pm.PackageInstaller class and its nested classes in the Android API. The active install session will write the embedded APK file to the /data/app directory, but the app will not be installed since third-party applications cannot programmatically install apps. Samsung has modified AOSP in order to accelerate the parsing of APKs by introducing the com.android.server.pm.PackagePrefetcher class and its nested classes. These classes will parse the APKs present in the /data/app directory and other directories, even if the app is not actually installed. The embedded APK that was written to the /data/app directory via the active install session has a very large but valid AndroidManifest.xml file. Specifically, the AndroidManifest.xml file contains a very large string value for the name of a permission-tree that it declares. When system_server tries to parse the APK file of the embedded app from the active install session, it will crash due to an uncaught error (i.e., java.lang.OutOfMemoryError) or an uncaught exception (i.e., std::bad_alloc) because of memory constraints. The Samsung Android device will encounter a soft reboot due to a system_server crash, and this action will keep repeating since parsing the APKs in the /data/app directory as performed by the system_server process is part of the normal boot process. The Samsung ID is SVE-2016-6917.
Vulnerable Configurations
| Part | Description | Count |
|---|---|---|
| OS | 4 |
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Buffer Overflow via Environment Variables This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
- Server Side Include (SSI) Injection An attacker can use Server Side Include (SSI) Injection to send code to a web application that then gets executed by the web server. Doing so enables the attacker to achieve similar results to Cross Site Scripting, viz., arbitrary code execution and information disclosure, albeit on a more limited scale, since the SSI directives are nowhere near as powerful as a full-fledged scripting language. Nonetheless, the attacker can conveniently gain access to sensitive files, such as password files, and execute shell commands.
- Cross Zone Scripting An attacker is able to cause a victim to load content into their web-browser that bypasses security zone controls and gain access to increased privileges to execute scripting code or other web objects such as unsigned ActiveX controls or applets. This is a privilege elevation attack targeted at zone-based web-browser security. In a zone-based model, pages belong to one of a set of zones corresponding to the level of privilege assigned to that page. Pages in an untrusted zone would have a lesser level of access to the system and/or be restricted in the types of executable content it was allowed to invoke. In a cross-zone scripting attack, a page that should be assigned to a less privileged zone is granted the privileges of a more trusted zone. This can be accomplished by exploiting bugs in the browser, exploiting incorrect configuration in the zone controls, through a cross-site scripting attack that causes the attackers' content to be treated as coming from a more trusted page, or by leveraging some piece of system functionality that is accessible from both the trusted and less trusted zone. This attack differs from "Restful Privilege Escalation" in that the latter correlates to the inadequate securing of RESTful access methods (such as HTTP DELETE) on the server, while cross-zone scripting attacks the concept of security zones as implemented by a browser.
- Cross Site Scripting through Log Files An attacker may leverage a system weakness where logs are susceptible to log injection to insert scripts into the system's logs. If these logs are later viewed by an administrator through a thin administrative interface and the log data is not properly HTML encoded before being written to the page, the attackers' scripts stored in the log will be executed in the administrative interface with potentially serious consequences. This attack pattern is really a combination of two other attack patterns: log injection and stored cross site scripting.
- Command Line Execution through SQL Injection An attacker uses standard SQL injection methods to inject data into the command line for execution. This could be done directly through misuse of directives such as MSSQL_xp_cmdshell or indirectly through injection of data into the database that would be interpreted as shell commands. Sometime later, an unscrupulous backend application (or could be part of the functionality of the same application) fetches the injected data stored in the database and uses this data as command line arguments without performing proper validation. The malicious data escapes that data plane by spawning new commands to be executed on the host.