Evidence used
- No CISA KEV confirmation is currently recorded.
- Exploitation requires an existing local or physical foothold with privileges.
- EPSS is 0.40% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-83926High confidence
Windows Hello Security Feature Bypass Vulnerability
Microsoft · Windows 10 Version 1809
4.4MediumCVSS 3.1
Scheduled
Patch availableMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Low, lowered one band.downgradedsince 13 Oct 2026
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict local access and enforce least privilege on affected hosts.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Microsoft Windows 10 Version 1809 and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available01
What, why and how
Improper certificate validation in Windows Hello allows an authorized attacker to bypass a security feature locally.
What
Improper certificate validation in Windows Hello allows an authorized attacker to bypass a security feature locally.
Why
The product does not validate, or incorrectly validates, a certificate.
How
An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
Improper certificate validation in Windows Hello allows an authorized attacker to bypass a security feature locally.
Why
The product does not validate, or incorrectly validates, a certificate.
How
An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- local access → Improper Certificate Validation → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Local
- Privileges required
- High: elevated access is required
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-295 ↗
CWE-295: Improper Certificate Validation. The product does not validate, or incorrectly validates, a certificate.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:CCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.INoneIntegrity impact: No direct loss is represented by this metric.ANoneAvailability impact: No direct loss is represented by this metric.- Post-exploitation / living off the land
- The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Patch available
- Affected
- Windows 10 Version 1809: 10.0.17763.0 < 10.0.17763.9376
- Windows 10 Version 21H2: 10.0.19044.0 < 10.0.19044.7807
- Windows 10 Version 22H2: 10.0.19045.0 < 10.0.19044.7807
- Windows 11 version 23H2: 10.0.22631.0 < 10.0.22631.7652
- Windows 11 Version 23H2: 10.0.22631.0 < 10.0.22631.7652
- Windows 11 Version 24H2: 10.0.26100.0 < 10.0.26100.9711
- Windows 11 Version 25H2: 10.0.26200.0 < 10.0.26200.9711
- Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.3231
- Windows 11 Version 26H2: 10.0.26300.0 < 10.0.26300.9711
- Windows Server 2019: 10.0.17763.0 < 10.0.17763.9376
- Windows Server 2019 (Server Core installation): 10.0.17763.0 < 10.0.17763.9376
- Windows Server 2022: 10.0.20348.0 < 10.0.20348.5761
- Windows Server 2025: 10.0.26100.0 < 10.0.26100.33650
- Windows Server 2025 (Server Core installation): 10.0.26100.0 < 10.0.26100.33650
- Action
- Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
- Workaround
- No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
Official vendor articles7 stored documents
Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.
- October 13, 2026—KB5126646 (OS Build 26100.33650) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5126646 (OS Build 26100.33650) Applies To Windows Server 2025, all editions This cumulative update for Windows Server 2025 (KB5126646), includes the latest security fixes and improvements, along with non-security updates from last month’s optional preview release. Visit the Windows release health da
- October 13, 2026—KB5126651 (OS Build 17763.9376) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5126651 (OS Build 17763.9376) Applies To Windows Server 2019 Win 10 Ent LTSC 2019 Summary This article lists the security issues and quality improvements included in this cumulative security update. Windows Server 2019 Windows 10, version 1809 Applies to: Windows Server 2019 This security update i
- October 13, 2026—KB5126653 (OS Build 22621.7652) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5126653 (OS Build 22621.7652) Applies To Windows 11 version 23H2, all editions This cumulative update for Windows 11, version 23H2 (KB5126653), includes the latest security fixes and improvements, along with non-security updates from last month’s optional preview release. Visit the Windows release h
- October 13, 2026—KB5126655 (OS Build 20348.5761) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5126655 (OS Build 20348.5761) Applies To Windows Server 2022 This cumulative update for Windows Server 2022 (KB5126655), includes the latest security fixes and improvements, along with non-security updates from last month’s optional preview release. Visit the Windows release health dashboard for the
- October 13, 2026—KB5126657 (OS Builds 19045.7807 and 19044.7807) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5126657 (OS Builds 19045.7807 and 19044.7807) Applies To Windows 10 ESU Windows 10 Enterprise LTSC 2021 Windows 10 IoT Enterprise LTSC 2021 Important Free support for Windows 10 Enterprise LTSC 2021 ends on January 12, 2027. To learn about continuing support, see Plan for Windows 10 Enterprise LTSC
- October 13, 2026—KB5127646 (OS Build 28000.3231) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5127646 (OS Build 28000.3231) Applies To Windows 11 version 26H1, all editions This cumulative update for Windows 11, version 26H1 (KB5127646) includes the latest security fixes and improvements, along with non-security updates from last month's optional preview release. Visit the Windows release he
- October 13, 2026—KB5127648 (OS Builds 26300.9711, 26200.9711 and 26100.9711) | Microsoft Support →Original publisher ↗Searchable text snapshot · Captured 14 Oct 2026October 13, 2026—KB5127648 (OS Builds 26300.9711, 26200.9711 and 26100.9711) Applies To Windows 11 version 26H2, all editions Windows 11 version 25H2, all editions Windows 11 version 24H2, all editions Want a quick overview?: Watch the Windows 11 release note video for this update. Announcements and messages This sec
04
Evidence and provenance
Published 13 Oct 2026 · Last source change 14 Oct 2026, 17:51 UTC · CWE-295 · Improper Certificate Validation
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-10-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-99440
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceOther authority
NVD statusNVD awaiting enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- ENISA EUVD mappingEUVD-2026-99440 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2026-99440"}
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
- CVSS scoreCVSS vector changed while the displayed base score remained 4.4.CNA ↗
- Before
- 4.4 (CVSS 3.1 · CNA · CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N)
- After
- 4.4 (CVSS 3.1 · CNA · CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C)
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.