CVE-2021-34527: Used in ransomware campaigns — CISA KEV

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;

01What CISA says about this vulnerability

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…

02Required action — verbatim from CISA

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

03Notes & references

• msrc.microsoft.com — https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527
• packetstormsecurity.com — http://packetstormsecurity.com/files/167261/Print-Spooler-Remote-DLL-Injection.h…
• portal.msrc.microsoft.com — https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-3452…
• www.kb.cert.org — https://www.kb.cert.org/vuls/id/383432
• www.vicarius.io — https://www.vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-detection-s…
• www.vicarius.io — https://www.vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-mitigation-…
• www.cisa.gov — https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-…

04SARA's analyst layer — why this matters

This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.

05Affected products (summary)

No structured affected-product list available — see references below for vendor advisories.

06Detection

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection:

Open in Sigma generator →