BlueHammer
BlueHammer (CVE-2026-33825) is a local elevation-of-privilege vulnerability in Microsoft Defender. Microsoft describes the issue as insufficient granularity of access control that allows an authorized attacker to elevate privileges locally. Supporting reporting indicates the exploit abuses the Microsoft Defender signature/update workflow and a TOCTOU race condition involving Defender’s MsMpEng service running as SYSTEM. Public technical descriptions state the exploit downloads a Defender signature package (mpam-fe), stages extracted Defender files in a temporary directory, and uses mechanisms including Volume Shadow Copy, Cloud Files callbacks, oplocks, and path/junction manipulation to cause privileged Defender operations to act on attacker-controlled targets. Reported outcomes include exposure of the SAM, SYSTEM, and SECURITY hives, access to local account password hashes, and in some exploit variants causing MsMpEng to write an attacker-controlled payload into a protected system path.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (5 hidden).
Small Windows-focused exploit repository for CVE-2026-33825 containing a single substantive source file, src/main.cpp, built with CMake. The code is a local privilege-escalation style PoC rather than a remote exploit. It uses low-level Windows and NT native APIs from ntdll.dll, plus Cloud Files API headers/libraries, to manipulate filesystem objects, enumerate object-manager directories, and set reparse points/mount points. The exploit workflow appears to prepare filesystem redirection primitives, race or coerce privileged file operations, then open \??\C:\Windows\System32\TieringEngineService.exe with FILE_SUPERSEDE semantics. After successful overwrite/placement, it copies its own executable into %WINDIR%\System32\TieringEngineService.exe and invokes LaunchTierManagementEng() to trigger execution. Repository structure is minimal: CMakeLists.txt for building, a short README naming CVE-2026-33825, and one large C++ implementation file. No network communication, C2, or external URLs are present; the exploit is entirely local and centered on Windows filesystem/object-manager abuse and privileged binary planting.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
162 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Microsoft Defender privilege escalation vulnerability, dubbed BlueHammer, that was publicly disclosed before patches were available and later confirmed by CISA as exploited in ransomware campaigns.
A high-severity local privilege escalation vulnerability in Microsoft Defender caused by insufficient granularity of access control, allowing an authorized local attacker to access the SAM database, escalate to SYSTEM privileges, and potentially take full control of the affected system.
A previously disclosed Microsoft vulnerability referenced as one of several zero-days published by the same researcher; no further technical details are provided in the content.
A Microsoft Defender vulnerability previously disclosed by Chaotic Eclipse and since patched by Microsoft.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.