SecBoard
Zurück zur CVE-Übersicht

CVE-2021-34527

HIGH(8.8)KEV — Aktiv ausgenutzt

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Risk Signal Score82/100 — KRITISCH
  • CVSS 8.8 — Hoch
  • EPSS 100% — sehr wahrscheinlich ausgenutzt
  • Im CISA KEV-Katalog (aktiv ausgenutzt)

CISA KEV

Bestätigt ausgenutzt

EPSS-Score

99.8%

Exploit-Wahrscheinlichkeit (30 Tage)

CVSS Score

8.8

Technische Schwere

SecBoard-Einordnung

CVE-2021-34527 ist eine () Schwachstelle im Windows Print Spooler Dienst. Sie ermöglicht es einem Angreifer, durch unsachgemäße privilegierte Dateivorgänge beliebigen Code mit SYSTEM-Rechten auszuführen. Dies kann zur Installation von Programmen, Datenmanipulation oder der Erstellung neuer Benutzerkonten mit vollen Rechten führen.

KI-gestützte Einordnung auf Basis der NVD-Daten.

Beschreibung

A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged file operations. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. UPDATE July 7, 2021: The security update for Windows Server 2012, Windows Server 2016 and Windows 10, Version 1607 have been released. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. If you are unable to install these updates, see the FAQ and Workaround sections in this CVE for information on how to help protect your system from this vulnerability. In addition to installing the updates, in order to secure your system, you must confirm that the following registry settings are set to 0 (zero) or are not defined (Note: These registry keys do not exist by default, and therefore are already at the secure setting.), also that your Group Policy setting are correct (see FAQ): HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint NoWarningNoElevationOnInstall = 0 (DWORD) or not defined (default setting) UpdatePromptSettings = 0 (DWORD) or not defined (default setting) Having NoWarningNoElevationOnInstall set to 1 makes your system vulnerable by design. UPDATE July 6, 2021: Microsoft has completed the investigation and has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. If you are unable to install these updates, see the FAQ and Workaround sections in this CVE for information on how to help protect your system from this vulnerability. See also KB5005010: Restricting installation of new printer drivers after applying the July 6, 2021 updates. Note that the security updates released on and after July 6, 2021 contain protections for CVE-2021-1675 and the additional remote code execution exploit in the Windows Print Spooler service known as “PrintNightmare”, documented in CVE-2021-34527.

Erkennung & Indikatoren

Ausnutzung

Aktiv ausgenutzt (CISA KEV, in Ransomware-Kampagnen bekannt). Oeffentliche Exploits vorhanden: authentifizierter Aufruf von RpcAddPrinterDriverEx()/RpcAsyncAddPrinterDriver() laedt eine Angreifer-DLL von einem Remote-Share, Ausfuehrung als SYSTEM (PrintNightmare). Beleg: CERT/CC VU#383432, CISA KEV.

Behobene Versionen

  • Windows-Sicherheitsupdate ab 6. Juli 2021 einspielen (siehe KB5005010)

Threat-Hunting-Queries

Keine IOCs in den geprueften Quellen. Verhaltensbasiert aus der Schwachstellenklasse: der Print-Spooler-Dienst (spoolsv.exe) startet einen Kindprozess bzw. laedt eine DLL aus untypischem Pfad. Zusaetzlich spoolsv.exe-DLL-ImageLoads ausserhalb System32/Spooldriver-Pfaden pruefen.

Sentinel/Defender KQL

DeviceProcessEvents
| where InitiatingProcessFileName =~ "spoolsv.exe"
| where FileName in~ ("cmd.exe","powershell.exe","rundll32.exe","regsvr32.exe","wscript.exe","cscript.exe")
| project Timestamp, DeviceName, InitiatingProcessFileName, FileName, ProcessCommandLine, AccountName

Splunk SPL

index=* sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1 ParentImage="*\\spoolsv.exe" (Image="*\\cmd.exe" OR Image="*\\powershell.exe" OR Image="*\\rundll32.exe" OR Image="*\\regsvr32.exe")
| table _time host ParentImage Image CommandLine User

Sigma

title: Print Spooler startet Kindprozess (PrintNightmare CVE-2021-34527)
status: experimental
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    ParentImage|endswith: '\spoolsv.exe'
    Image|endswith:
      - '\cmd.exe'
      - '\powershell.exe'
      - '\rundll32.exe'
      - '\regsvr32.exe'
      - '\wscript.exe'
      - '\cscript.exe'
  condition: selection
level: high

Elastic ES|QL

FROM logs-* | WHERE process.parent.name == "spoolsv.exe" AND process.name IN ("cmd.exe","powershell.exe","rundll32.exe","regsvr32.exe") | KEEP @timestamp, host.name, process.parent.name, process.name, process.command_line

SecBoard-generated · behavioral · requires customization — Von SecBoard erzeugt und nicht in einer Zielumgebung validiert. Vor dem Einsatz an die eigene Protokollierung anpassen.

Betroffene Produkte

  • cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_11_21h2:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_11_22h2:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:*
  • cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
  • cpe:2.3:o:microsoft:windows_server_20h2:*:*:*:*:*:*:*:*

Referenzen