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Report · Bleeping ComputerAbout CVE-2026-33825Published

CISA: Windows BlueHammer flaw now exploited by ransomware gangs

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Authoritative record:CVE-2026-33825· High 7.8

Exploited in the wild · KEV due 6 May 2026 · public exploit available : upgrade to 4.18.26030.3011 now.

Data as of 13 Nov 2026, 23:53 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
KEV deadline
 US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
Patch
Available – fixed in 4.18.26030.3011
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 14 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CVSS exploit maturity: proof of concept public

  4. Exploited in the wild: evidence found.

    Listed in CISA KEV 8 days after disclosure

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by Microsoft Corporation

    , 21 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. In Threat Radar

    record ingested

    , 35 minutes after disclosure

  4. Added to CISA KEV (opens in a new tab)

    exploitation confirmed · ransomware use known

    , 8 days after disclosure

  5. KEV remediation due

    US federal deadline

    , 22 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Upgrade Microsoft Defender Antimalware Platform to 4.18.26030.3011.

Affected software

ProductAffectedFixed in
MicrosoftMicrosoft Defender Antimalware PlatformAffected
  • >=4.0.0.0 <4.18.26030.3011
Fixed in
  • 4.18.26030.3011

AI-suggested

Microsoft released an official patch for BlueHammer on April 14, 2026, as part of the April 2026 Patch Tuesday updates. CISA has mandated that federal agencies apply this patch by May 7, 2026. Organizations should ensure that all Windows systems running Microsoft Defender are updated with the April 2026 security patches to mitigate this vulnerability. No additional mitigations are specified beyond applying the official fix.

Description

The BlueHammer vulnerability (CVE-2026-33825) is a high-severity local privilege escalation flaw in Microsoft Defender that allows authorized local attackers to elevate privileges to SYSTEM by accessing the Security Account Manager (SAM) database. Initially exploited as a zero-day, it has now been confirmed by CISA to be actively exploited by ransomware gangs. Microsoft patched the vulnerability on April 14, 2026, and CISA has mandated federal agencies to apply the patch promptly. The flaw was publicly disclosed with proof-of-concept code by a security researcher in April 2026.

References

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