FBI, CISA Warn of Russian Hackers Exploiting MFA and PrintNightmare Bug
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2021-34527 | PrintNightmare: Remote Code Execution in Microsoft Windows Print Spooler CVE-2021-34527, widely known as 'PrintNightmare', is a remote code execution flaw in the Microsoft Windows Print Spooler service, which improperly performs privileged file operations such as loading printer driver DLLs. An attacker with low-level access who can reach a machine's spooler, for example a domain user able to add a printer connection via Point and Print, can induce the SYSTEM-privileged service to load an attacker-controlled DLL with no user interaction required (CVSS:3.1 vector AV:N/AC:L/PR:L/UI:N). Successful exploitation yields arbitrary code execution as SYSTEM, letting the attacker install programs, view, change or delete data, and create new accounts with full user rights, effectively achieving complete host compromise. The flaw affects all supported Windows client and server releases in the CISA data, Windows 10 from 1507 through 22H2, Windows 11, Windows RT 8.1, and Windows Server 2008, 2012 and 2016, wherever the Print Spooler service is running. Exploitation is confirmed in the wild: the bug was added to CISA's Known Exploited Vulnerabilities catalog on 2021-11-03 with known ransomware use, the FBI and CISA have warned of Russian actors exploiting it, and EPSS places the 30-day exploitation probability at 99.8%. Do: Install the July 2021 security updates immediately, released July 6, 2021 with additional updates on July 7 for Windows Server 2012, Windows Server 2016 and Windows 10 version 1607, and review KB5005010 for restricting installation of new printer drivers after applying the July 6 updates. Where patching is delayed, disable the Print Spooler service on hosts that do not need printing or restrict Point and Print, and verify that NoWarningNoElevationOnInstall and UpdatePromptSettings under HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint are set to 0 or not defined (these keys do not exist by default, which is the secure state; NoWarningNoElevationOnInstall = 1 makes the system vulnerable by design). Prioritize domain controllers and servers with exposed spoolers, and hunt… | 8.8 | 100% | KEV ransomware PoC ×3 |
| masshundreds of millions of Windows systems (order of magnitude 10^8) |
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Ravie LakshmananMar 16, 2022
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) and the Federal Bureau of Investigation (FBI) have released a joint advisory warning that Russia-backed threat actors hacked the network of an unnamed non-governmental entity by exploiting a combination of flaws.
"As early as May 2021, Russian state-sponsored cyber actors took advantage of a misconfigured account set to default [multi-factor authentication] protocols at a non-governmental organization (NGO), allowing them to enroll a new device for MFA and access the victim network," the agencies said.
"The actors then exploited a critical Windows Print Spooler vulnerability, 'PrintNightmare' (CVE-2021-34527) to run arbitrary code with system privileges."
The attack was pulled off by gaining initial access to the victim organization via compromised credentials – obtained by means of a brute-force password guessing attack – and enrolling a new device in the organization's Duo MFA.
It's also noteworthy that the breached account was un-enrolled from Duo due to a long period of inactivity, but had not yet been disabled in the NGO's Active Directory, thereby allowing the attackers to escalate their privileges using the PrintNightmare flaw and disable the MFA service altogether.
"As Duo's default configuration settings allow for the re-enrollment of a new device for dormant accounts, the actors were able to enroll a new device for this account, complete the authentication requirements, and obtain access to the victim network," the agencies explained.
Turning off MFA, in turn, allowed the state-sponsored actors to authenticate to the NGO's virtual private network (VPN) as non-administrator users, connect to Windows domain controllers via Remote Desktop Protocol (RDP), and obtain credentials for other domain accounts.
In the final stage of the attack, the newly compromised accounts were subsequently utilized to move laterally across the network to siphon data from the organization's cloud storage and email accounts.
To mitigate such attacks, both CISA and FBI are recommending organizations to enforce and review multi-factor authentication configuration policies, disable inactive accounts in Active Directory, and prioritize patching for known exploited flaws.
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