Very High
CVE-2021-1675
CVE-2021-1675
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Technical Analysis
Vulnerability
This was originally classified as a Local Priv Escalation, however recent POC code has been released that enabled a domain authenticated user to remotely escalate to SYSTEM on vulnerable services
Exploit Code
There are several functional exploits available on Github after the initial repository was removed by the authors.
- https://github.com/afwu/PrintNightmare – A windows binary exploit
- https://github.com/cube0x0/CVE-2021-1675 – Python3 using a modified version of impacket
Mitigation
Initial testing shows that the patches released are not sufficient to stop this exploit. It has been tested in Server 2016 and Server 2019.
Disable the print spooler can prevent exploitation.
Event logs can be found for both successful and non-successful exploit attempts in some situations.
Sigma rules can be found: https://github.com/SigmaHQ/sigma/pull/1592
Technical Analysis
Microsoft has just assigned a new CVE to PrintNightmare (CVE-2021-34527) and published a security guide about this vulnerability. This guide contains a summay, exploitability, workarounds and a FAQ:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527
Future patches will be released at that address.
Technical Analysis
Vulnerability
Can be used as LPE and RCE. Code will run as SYSTEM.
Possible temporary mitigations
Patch for CVE-2021-1675 published on the 08.06.2021 mitigates exploitation if User is not an admin and computer is not a domain controller.
To mitigate lateral movement a GPO can be used to disabled connections to spooler RPC service https://github.com/LaresLLC/CVE-2021-1675
To mitigate LPE and RCE a ACL for the printer driver can be set https://blog.truesec.com/2021/06/30/fix-for-printnightmare-cve-2021-1675-exploit-to-keep-your-print-servers-running-while-a-patch-is-not-available/
Disabling the spooler service is also an theoretical option, but might come at a high operational cost.
Technical Analysis
Proof-of-concept exploit code has been published online today for a vulnerability in the Windows Print Spooler service that can allow a total compromise of Windows systems.
Source: https://therecord.media/poc-released-for-dangerous-windows-printnightmare-bug/
It’s been reported that it’s possible that a threat actor can bypass creating these event IDs (808-The print spooler failed to load a plug-in module and 31017-Microsoft-Windows-SmbClient/Security ) by using a legit Windows print driver — for example one of the Windows SDK examples — and piggy backing malicious code off the files.
Technical Analysis
Rapid7 researchers have confirmed that a fully patched (as of June 2021) Windows Server 2019 is exploitable with at least one of the public exploits. There’s still a lot of confusion in the community about what exactly is exploitable and why (e.g., permissions requirements), but don’t let the complexity inherent to these researcher conversations convince you NOT to act. Disable the print spooler, quickly. More info: https://www.rapid7.com/blog/post/2021/06/30/cve-2021-1675-printnightmare-patch-does-not-remediate-vulnerability/
CVSS V3 Severity and Metrics
General Information
Vendors
- microsoft
Products
- windows 10 1507,
- windows 10 1607,
- windows 10 1809,
- windows 10 1909,
- windows 10 2004,
- windows 10 20h2,
- windows 10 21h1,
- windows 7 -,
- windows 8.1 -,
- windows rt 8.1 -,
- windows server 2004,
- windows server 2008 -,
- windows server 2008 r2,
- windows server 2012 -,
- windows server 2012 r2,
- windows server 2016,
- windows server 2019
Metasploit Modules
Exploited in the Wild
References
Miscellaneous
