Faiblesses connexes
CWE-ID |
Nom de la faiblesse |
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. |
|
Métriques
Métriques |
Score |
Gravité |
CVSS Vecteur |
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 MetricsThe 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. 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. 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. 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. The vulnerable system can be exploited without interaction from any user. Base: Scope MetricsAn 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. 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 MetricsThe 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. 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. 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. 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 MetricsThe 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 est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.
Score EPSS
Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.
Percentile EPSS
Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
Informations sur l'Exploit
Exploit Database EDB-ID : 45379
Date de publication : 2018-09-10 22h00 +00:00
Auteur : Google Security Research
EDB Vérifié : 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
Références