module

Microsoft Exchange Server ChainedSerializationBinder Deny List Typo RCE

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Disclosed
2021-12-09
Created
2022-02-24

Description

This vulnerability allows remote attackers to execute arbitrary code
on Exchange Server 2019 CU10 prior to Security Update 3, Exchange Server 2019 CU11
prior to Security Update 2, Exchange Server 2016 CU21 prior to
Security Update 3, and Exchange Server 2016 CU22 prior to
Security Update 2.

Note that authentication is required to exploit this vulnerability.

The specific flaw exists due to the fact that the deny list for the
ChainedSerializationBinder had a typo whereby an entry was typo'd as
System.Security.ClaimsPrincipal instead of the proper value of
System.Security.Claims.ClaimsPrincipal.

By leveraging this vulnerability, attacks can bypass the
ChainedSerializationBinder's deserialization deny list
and execute code as NT AUTHORITY\SYSTEM.

Tested against Exchange Server 2019 CU11 SU0 on Windows Server 2019,
and Exchange Server 2016 CU22 SU0 on Windows Server 2016.

Authors

pwnforsp
zcgonvh
Microsoft Threat Intelligence Center
Microsoft Security Response Center
peterjson
testanull
Grant Willcox

Platform

Windows

Architectures

cmd, x86, x64

References

Module Options

To display the available options, load the module within the Metasploit console and run the commands ‘show options’ or ‘show advanced’:


    msf > use exploit/windows/http/exchange_chainedserializationbinder_denylist_typo_rce
    msf exploit(exchange_chainedserializationbinder_denylist_typo_rce) > show targets
        ...targets...
    msf exploit(exchange_chainedserializationbinder_denylist_typo_rce) > set TARGET < target-id >
    msf exploit(exchange_chainedserializationbinder_denylist_typo_rce) > show options
        ...show and set options...
    msf exploit(exchange_chainedserializationbinder_denylist_typo_rce) > exploit
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