CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability
Noroxi assessment
Priority: Now (action score 82/100)
- CISA has confirmed exploitation in the wild (Jan 26, 2026). Remediation deadline for US federal agencies: Feb 16, 2026.
- Probability of exploitation in the next 30 days: 70.8% (FIRST EPSS); higher than 99.4% of all records.
- Someone with local access to the system can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
- Fixed version: Microsoft 365 Apps for Enterprise for 32-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft 365 Apps for Enterprise for 64-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft Office 2016 (32-bit edition) 16.0.5539.1001.
Patch today or shut off access. Upgrade to Microsoft 365 Apps for Enterprise for 32-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft 365 Apps for Enterprise for 64-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft Office 2016 (32-bit edition) 16.0.5539.1001 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
- Published
- Jan 26, 2026
- Updated
- Jul 30, 2026
- EPSS
- 70.8% · 99th percentile
- CWE
- CWE-807
Report tools
Action score
82
Patch today or shut off access.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 30 / 30 · Listed
- EPSS
- 21 / 30 · 70.8%
CISA SSVC decision
- Exploitation
- active
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · microsoft
- 7.8
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Actively exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on Jan 26, 2026. That signals real attacks, not theory.
Remediation deadline for US federal agencies: Feb 16, 2026.
Get told when this record changes
- In CISA KEV: exploitation in the wild confirmed
- Weaponized exploit exists
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
Is your version affected? Check itNoroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| microsoft | 365 apps | cpe:2.3:a:microsoft:365_apps |
| microsoft | office | cpe:2.3:a:microsoft:office |
| microsoft | office long term servicing channel | cpe:2.3:a:microsoft:office_long_term_servicing_channel |
Versions reported by the vendor
Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.
Microsoft Microsoft 365 Apps for Enterprise
- 16.0.1 and later · before https://aka.ms/OfficeSecurityReleasesaffected
Microsoft Microsoft Office 2016
- 16.0.0 and later · before 16.0.5539.1001affected
Microsoft Microsoft Office 2019
- 19.0.0 and later · before 16.0.10417.20095affected
Microsoft Microsoft Office LTSC 2021
- 16.0.1 and later · before https://aka.ms/OfficeSecurityReleasesaffected
Microsoft Microsoft Office LTSC 2024
- 16.0.0 and later · before https://aka.ms/OfficeSecurityReleasesaffected
Affected versions · NVD (5)
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- microsoft 365 appsall versions
- microsoft office2016
- microsoft office2019
- microsoft office long term servicing channel2021
- microsoft office long term servicing channel2024
Same product
microsoft: all recordsOther highest-scoring records for the same primary product.
- CVE-2023-23397Microsoft Outlook Elevation of Privilege VulnerabilityKEV98Now
- CVE-2024-21413Microsoft Outlook Remote Code Execution VulnerabilityKEV97Now
- CVE-2021-42292Microsoft Excel Security Feature Bypass VulnerabilityKEV74This week
Published before and after this one in the same product
- ← EarlierCVE-2026-20956Jan 13, 2026 · Microsoft Excel Remote Code Execution Vulnerability31Monitor
- ← EarlierCVE-2026-20957Jan 13, 2026 · Microsoft Excel Remote Code Execution Vulnerability31Monitor
- Later →CVE-2026-21258Feb 10, 2026 · Microsoft Excel Information Disclosure Vulnerability22Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Microsoft 365 Apps for Enterprise for 32-bit Systems | https://aka.ms/OfficeSecurityReleases · Click to Run | Microsoft (MSRC) |
| Microsoft 365 Apps for Enterprise for 64-bit Systems | https://aka.ms/OfficeSecurityReleases · Click to Run | Microsoft (MSRC) |
| Microsoft Office 2016 (32-bit edition) | 16.0.5539.1001 · KB5002713 | Microsoft (MSRC) |
| Microsoft Office 2016 (64-bit edition) | 16.0.5539.1001 · KB5002713 | Microsoft (MSRC) |
| Microsoft Office 2019 for 32-bit editions | 16.0.10417.20095 · Click to Run | Microsoft (MSRC) |
| Microsoft Office 2019 for 64-bit editions | 16.0.10417.20095 · Click to Run | Microsoft (MSRC) |
| Microsoft Office LTSC 2021 for 32-bit editions | https://aka.ms/OfficeSecurityReleases · Click to Run | Microsoft (MSRC) |
| Microsoft Office LTSC 2021 for 64-bit editions | https://aka.ms/OfficeSecurityReleases · Click to Run | Microsoft (MSRC) |
| Microsoft Office LTSC 2024 for 32-bit editions | https://aka.ms/OfficeSecurityReleases · Click to Run | Microsoft (MSRC) |
| Microsoft Office LTSC 2024 for 64-bit editions | https://aka.ms/OfficeSecurityReleases · Click to Run | Microsoft (MSRC) |
Exploit status
Weaponized
A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.
Evidence
- Proof-of-concept repository on GitHub ×12
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Proof-of-concept repository on GitHub | 12 repositories | 2026-01-27 → 2026-07-23 |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- CISA KEV-1 d
- Published
- First PoCsame day
- TodayNov 14, 2026+292 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-2151415 days apartMicrosoft Word Security Feature Bypass VulnerabilityKEV61This week
- CVE-2026-88210260 days apartMicrosoft Office Word Security Feature Bypass Vulnerability31Monitor
- CVE-2026-108433262 days apartMicrosoft Office Word Security Feature Bypass Vulnerability31Monitor
Not on record for this CVE: patch commit or PR link · researcher credit · public bounty program.
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- No account or password is required.
- A user must open a link or visit a page.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-807 · Reliance on Untrusted Inputs in a Security DecisionCVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log (1)
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (3 more)Show less
- www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability
- www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509
Vendor advisories and official records. Exploit/PoC links are deliberately left out.