CISA: Windows BlueHammer flaw now exploited by ransomware gangs
Source Bleeping Computer
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
- 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:CExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 14 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 8 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by Microsoft Corporation
, 21 days before disclosure
CVE published
on cve.org
, t = 0
In Threat Radar
record ingested
, 35 minutes after disclosure
Added to CISA KEV (opens in a new tab)
exploitation confirmed · ransomware use known
, 8 days after disclosure
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
| Product | Affected | Fixed in |
|---|---|---|
| MicrosoftMicrosoft Defender Antimalware Platform | Affected
| Fixed in
|
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.