Wednesday, August 31, 2022

Micropatches for Local Privilege Escalation in LSASS (CVE-2022-30166)



by Mitja Kolsek, the 0patch Team

Update 9/1/2022: Micropatches for Local Privilege Escalation in LSASS (CVE-2022-30166) that were issued yesterday were reported to cause authentication problems with SharePoint and Remote Desktop Gateway Service. After successfully reproducing the issue these patches have just just revoked, and will be automatically disabled on all systems within 60 minutes. No action is needed on 0patch users' and administrator' end while we're working on issuing corrected patches.

Update 9/20/2022: After reproducing functional problems caused by our original micropatches we have now issued new ones. We'd like to thank all customers who promptly reported problems and helped us reproduce them. No action is needed on 0patch users' and administrator' end to have the new patches applied.


June 2022 Windows Updates brought a fix for a local privilege escalation in Local Security Authority Subsystem Service (LSASS), discovered by James Forshaw of Google Project Zero. James published details and a POC on July 14.

The vulnerability allows a local non-admin attacker to use a certain type of impersonation (specifically, impersonating a token at identification level) to get the service running as Local System to enumerate the ticket cache not only for the requesting user but also for the Local System account. With this information, the attacker could elevate their privileges on the local system.

Microsoft assigned this issue CVE-2022-30166 and fixed it by creating an "anonymous" impersonation when the original attempt at impersonation fails; as a result, a malicious request ends up returning only requesting user's ticket cache.

Our micropatch with 18 CPU instructions is logically equivalent to Microsoft's:

MODULE_PATH "..\AffectedModules\lsasrv.dll_10.0.19041.1415_Win10-2004_64-bit_u202112\lsasrv.dll"
VULN_ID 7441

    PIT lsasrv!0x145f0,ntdll!NtClose
        mov byte[rdi+0x11], 1     ;original overwritten code
        mov [rdi+0x14], eax       ;original overwritten code
        cmp eax, 1                ;check current tokens impersonation level. 1 == ANONYMOUS
        jne END                   ;if it is ANONYMOUS nothing needs to be done and we
                                  ;skip the patch
        mov rcx, [rbx+0x0c0]      ;move current token handle to rcx so we can close it
        sub rsp, 0x20             ;create shadowspace with additional 0x8 bytes to
                                  ;align the stack
        call PIT_NtClose          ;close the token handle
        add rsp, 0x20             ;delete the created shadowspace
        mov qword[rbx+0x0c0], 0x0 ;overwrite the old handle with 0x0
        mov rcx, rdi              ;move SECPKG_CLIENT_INFO_EX to rcx
        lea rdx, [rbx+0x0c0]      ;move new handle pointer to rdx for output
        mov qword[rcx], 0x3e6     ;move LsapAnonymousLogonId to rcx pointer
        push 0x000003e6           ;push LsapAnonymousLogonId to stack so we can use the
        lea rcx, [rsp]            ;move the pointer to LsapAnonymousLogonId into rcx
        sub rsp, 0x28             ;create shadowsapce
        call PIT_0x145f0          ;call LsapOpenTokenByLogonId to get a new anonymous
        add rsp, 0x30             ;clear shadowspace and account for the push
        mov rax, 1                ;move 1 to eax as some versions of this dll need it
                                  ;and we don't need the return value


This video demonstrates the effect of our micropatch. With 0patch disabled, the POC obtains and displays the token cache of both the current user and Local System; with 0patch enabled, only user's token cache is accessible to the local non-admin user.


The micropatch was written for the following Versions of Windows with all available Windows Updates installed:

  1. Windows 10 v2004
  2. Windows 10 v1909
  3. Windows 10 v1903
  4. Windows 10 v1809
  5. Windows 10 v1803
  6. Windows 7 (no ESU, ESU year 1, ESU year 2)
  7. Windows Server 2008 R2 (no ESU, ESU year 1, ESU year 2)

This micropatch has already been distributed to all online 0patch Agents with a PRO or Enterprise license. To obtain the micropatch and have it applied on your computers along with our other micropatches, create an account in 0patch Central, install 0patch Agent and register it to your account with a PRO or Enterprise subscription. Note that no computer restart is needed for installing the agent or applying/un-applying any 0patch micropatch. 

To learn more about 0patch, please visit our Help Center

We'd like to thank James Forshaw for publishing their analysis and providing a proof-of-concept that allowed us to reproduce the vulnerability and create a micropatch. We also encourage security researchers to privately share their analyses with us for micropatching.

No comments:

Post a Comment