CVE-2018-9488 : Detail

CVE-2018-9488

7.8
/
High
Authorization problems
A01-Broken Access Control
0.05%V3
Local
2018-11-06
17h00 +00:00
2024-09-17
01h50 +00:00
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CVE Descriptions

In the SELinux permissions of crash_dump.te, there is a permissions bypass due to a missing restriction. This could lead to a local escalation of privilege, with System privileges needed. User interaction is not needed for exploitation. Product: Android Versions: Android-8.0 Android-8.1 Android-9.0 Android ID: A-110107376.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-863 Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Metrics

Metrics Score Severity CVSS Vector Source
V3.0 7.8 HIGH CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Local

A vulnerability exploitable with Local access means that the vulnerable component is not bound to the network stack, and the attacker's path is via read/write/execute capabilities. In some cases, the attacker may be logged in locally in order to exploit the vulnerability, otherwise, she may rely on User Interaction to execute a malicious file.

Attack Complexity

This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker is authorized with (i.e. requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.

User Interaction

This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges.

Scope

Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports.

Unchanged

An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same.

Base: Impact Metrics

The Impact metrics refer to the properties of the impacted component.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability.

Environmental Metrics

nvd@nist.gov
V2 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P nvd@nist.gov

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

Exploit information

Exploit Database EDB-ID : 45379

Publication date : 2018-09-10 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

After reporting https://bugs.chromium.org/p/project-zero/issues/detail?id=1583 (Android ID 80436257, CVE-2018-9445), I discovered that this issue could also be used to inject code into the context of the zygote. Additionally, I discovered a privilege escalation path from zygote to init; that escalation path is why I'm filing a new bug. Essentially, the privilege escalation from zygote to init is possible because system/sepolicy/private/zygote.te contains the following rule: allow zygote self:capability sys_admin; (On the current AOSP master branch, the rule looks slightly different, but it's still there.) This rule allows processes in the zygote domain to use the CAP_SYS_ADMIN capability, if they have such a capability. The zygote has the capability and uses it, e.g. to call umount() and to install seccomp filters without setting the NO_NEW_PRIVS flag. CAP_SYS_ADMIN is a bit of a catch-all capability: If kernel code needs to check that the caller has superuser privileges and none of the capability bits fit the particular case, CAP_SYS_ADMIN is usually used. The capabilities(7) manpage has a long, but not exhaustive, list of things that this capability permits: http://man7.org/linux/man-pages/man7/capabilities.7.html One of the syscalls that can be called with CAP_SYS_ADMIN and don't have significant additional SELinux hooks is pivot_root(). This syscall can be used to switch out the root of the current mount namespace and, as part of that, change the root of every process in that mount namespace to the new namespace root (unless the process already had a different root). The exploit for this issue is in zygote_exec_target.c, starting at "if (unshare(CLONE_NEWNS))". The attack is basically: 1. set up a new mount namespace with a root that is fully attacker-controlled 2. execute crash_dump64, causing an automatic transition to the crash_dump domain 3. the kernel tries to load the linker for crash_dump64 from the attacker-controlled filesystem, resulting in compromise of the crash_dump domain 4. from the crash_dump domain, use ptrace() to inject syscalls into vold 5. from vold, set up a loop device with an attacker-controlled backing device and mount the loop device over /sbin, without "nosuid" 6. from vold, call request_key() with a nonexistent key, causing a usermodehelper invocation to /sbin/request-key, which is labeled as init_exec, causing an automatic domain transition from kernel to init (and avoiding the "neverallow kernel *:file { entrypoint execute_no_trans };" aimed at stopping exploits using usermodehelpers) 7. code execution in the init domain Note that this is only one of multiple possible escalation paths; for example, I think that you could also enable swap on an attacker-controlled file, then modify the swapped-out data to effectively corrupt the memory of any userspace process that hasn't explicitly locked all of its memory into RAM. In order to get into the zygote in the first place, I have to trigger CVE-2018-9445 twice: 1. Use the bug to mount a "public volume" with a FAT filesystem over /data/misc. 2. Trigger the bug again with a "private volume" with a dm-crypt-protected ext4 filesystem that will be mounted over /data. To decrypt the volume, a key from /data/misc/vold/ is used. 3. Cause system_server to crash in order to trigger a zygote reboot. For this, the following exception is targeted: *** FATAL EXCEPTION IN SYSTEM PROCESS: NetworkStats java.lang.NullPointerException: Attempt to get length of null array at com.android.internal.util.FileRotator.getActiveName(FileRotator.java:309) at com.android.internal.util.FileRotator.rewriteActive(FileRotator.java:183) at com.android.server.net.NetworkStatsRecorder.forcePersistLocked(NetworkStatsRecorder.java:300) at com.android.server.net.NetworkStatsRecorder.maybePersistLocked(NetworkStatsRecorder.java:286) at com.android.server.net.NetworkStatsService.performPollLocked(NetworkStatsService.java:1194) at com.android.server.net.NetworkStatsService.performPoll(NetworkStatsService.java:1151) at com.android.server.net.NetworkStatsService.-wrap3(Unknown Source:0) at com.android.server.net.NetworkStatsService$HandlerCallback.handleMessage(NetworkStatsService.java:1495) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:164) at android.os.HandlerThread.run(HandlerThread.java:65) This exception can be triggered by sending >=2MiB (mPersistThresholdBytes) of network traffic to the device, then either waiting for the next periodic refresh of network stats or changing the state of a network interface. 4. The rebooting zygote64 does dlopen() on /data/dalvik-cache/arm64/system@framework@boot.oat, resulting in code execution in the zygote64. (For the zygote64 to get to this point, it's sufficient to symlink /data/dalvik-cache/arm64/system@framework@boot.{art,vdex} to their counterparts on /system, even though that code isn't relocated properly.) I have attached an exploit for the full chain, with usage instructions in USAGE. WARNING: As always, this exploit is intended to be used only on research devices that don't store user data. This specific exploit is known to sometimes cause data corruption. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/45379.zip

Products Mentioned

Configuraton 0

Google>>Android >> Version 8.0

Google>>Android >> Version 8.1

Google>>Android >> Version 9.0

References

https://www.exploit-db.com/exploits/45379/
Tags : exploit, x_refsource_EXPLOIT-DB