What is CVE-2026-33825?
A TOCTOU race condition in the Microsoft Defender Antimalware Platform update orchestrator allows a local low-privileged user to write an arbitrary file as SYSTEM via a symbolic-link hijack of the platform update staging directory. Proof-of-concept code was published to GitHub prior to Microsoft's advisory. No in-the-wild exploitation confirmed at release time, but the bug is trivial to weaponize and expected to appear in commodity post-exploitation toolkits within days.
The record classifies CVE-2026-33825 under weakness classes CWE-367, CWE-59. Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 197 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 7.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS (FIRST)
- 0.3% probability of exploitation in the next 30 days, higher than 32.0% of all scored CVEs
- CISA KEV
- Listed since 2026-04-22, federal remediation deadline 2026-05-06 — used in known ransomware campaigns
- Threadlinqs priority
- 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- Published
- 2026-04-14, last modified 2026-09-25
Is CVE-2026-33825 being exploited?
CISA added CVE-2026-33825 to the Known Exploited Vulnerabilities catalog on 2026-04-22, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-05-06 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2026-33825 is publicly available. 7 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 41 in the Threadlinqs vulnerability feed.
- Letlaka/redsun-bluehammer-undefend-detection-pack (github)
- 0xBlackash/CVE-2026-33825 (github)
- Joe1sn/CVE-2026-33825 (github)
- Bilal3755/Detecting_blue_hammer_vuln (github)
- kaleth4/CVE-2026-33825 (github)
- anasabugaddara-ux/defender-bluehammer-audit (github)
- trickest/cve (trickest)
Affected products and versions
- Microsoft: Defender Antimalware Platform
How to fix CVE-2026-33825
The record marks a vendor fix as available for CVE-2026-33825. Patch reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33825. Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33825. Because CVE-2026-33825 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-05-06. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-33825
12 tracked threats in the Threadlinqs corpus reference CVE-2026-33825, either in the campaign’s CVE list or as an indicator on the campaign record.
- BlueHammer (CVE-2026-33825) - Windows Defender Local Privilege Escalation, Exploited In The Wild and Added to CISA KEV — HIGH · 2026-10-24
- Q2 2026 Vulnerability and Exploit Landscape: Exploited AI-platform flaws (OpenClaw CVE-2026-25253, Dify CVE-2026-41948, Open WebUI CVE-2026-45386), Exchange CVE-2026-45501, and Linux kernel page-cache LPE exploit wave (Copy Fail, Dirty Frag) — HIGH · 2026-10-20
- NightmareEclipse Coordinated Disclosure Breach Campaign: 9+ Windows Zero-Days (CVE-2026-33825, CVE-2026-41091, CVE-2026-45498, CVE-2026-45585, CVE-2026-45586) Dumped Outside Responsible Disclosure and Weaponized in Real-World Intrusions — CRITICAL · 2026-08-04
- LegacyHive: Windows 0-Day Allows Standard Users to Load Another User's Registry Hive via User Profile Service — HIGH · 2026-07-15
- RoguePlanet: Microsoft Defender Elevation of Privilege Vulnerability (CVE-2026-50656) Patched — HIGH · 2026-07-10
- Windows Defender 0-Day Local Privilege Escalation "RoguePlanet" (Nightmare Eclipse Defender Exploit Series) — HIGH · 2026-06-10
- YellowKey & GreenPlasma — Unpatched Windows BitLocker Bypass & CTFMON LPE Zero-Days With Public PoC (Chaotic/Nightmare Eclipse) — CRITICAL · 2026-05-13
- Microsoft April 2026 Patch Tuesday — 163 CVEs / 88 Advisories (CVE-2026-32201 SharePoint Zero-Day Exploited In-The-Wild, CVE-2026-33825 Defender EoP Public PoC, CVE-2026-33824 IKE RCE CVSS 9.8, CVE-2026-33827 TCP/IP Wormable RCE) — CRITICAL · 2026-04-19
- Windows Defender Zero-Days (BlueHammer/RedSun/UnDefend) — Leaked Nightmare-Eclipse Exploits Weaponized In-The-Wild for SYSTEM LPE (CVE-2026-33825) — CRITICAL · 2026-04-17
- BlueHammer & RedSun: Windows Defender CVE-2026-33825 Zero-Day Remote Code Execution — CRITICAL · 2026-04-16
- CVE-2026-33825: Microsoft Defender Local Privilege Escalation via BlueHammer TOCTOU Race Condition — HIGH · 2026-04-15
- Microsoft April 2026 Patch Tuesday — 167 Flaws, 2 Zero-Days (SharePoint Spoofing CVE-2026-32201 + Defender EoP CVE-2026-33825) — CRITICAL · 2026-04-14
Sources
Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on .