What is CVE-2026-21510?

CVE-2026-21510 is Windows Shell Security Feature Bypass Vulnerability. The supplied enrichment data classifies it as Unclassified mapped to CWE-693 CWE-693.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Yes: CISA KEV signal present. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

Is there a public exploit?

5 public PoC repositories reported; 1 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-21510 using CVSS 8.8, EPSS 26%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

Publicly linked actor or ransomware signals in the supplied enrichment data: Nomad Panda (). Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Treat as emergency remediation because CISA KEV status is present. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

CISA KEVhighpublic exploit

CVE-2026-21510

CVE-2026-21510 — Windows Shell Security Feature Bypass Vulnerability

Q: Is it in CISA KEV?

Yes. The supplied enrichment data lists CVE-2026-21510 in CISA KEV with required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

Published Feb 10, 2026Updated Jun 17, 2026Sources: NVD, Microsoft (CNA), CISA, FIRST EPSS, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Confirmed

CISA KEV, listed Feb 10, 2026

EPSS

26%

ahead of 98% of scored CVEs

Affects

Microsoft

22 products listed

CVSS base

8.8

high · 2 sources

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

Active

none · proof-of-concept · active

Automatable

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

The vendor's own words where we have them.

Upgrade Windows 10 Version 1607 to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Federal deadline Mar 3, 2026 — passed 199 days ago

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Treat as emergency remediation because CISA KEV status is present.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Microsoft	Windows 10 Version 1607	10.0.14393.0 to < 10.0.14393.8868	Vulnerable
Microsoft	Windows 10 Version 1809	10.0.17763.0 to < 10.0.17763.8389	Vulnerable
Microsoft	Windows 10 Version 21H2	10.0.19044.0 to < 10.0.19044.6937	Vulnerable
Microsoft	Windows 10 Version 22H2	10.0.19045.0 to < 10.0.19045.6937	Vulnerable
Microsoft	Windows 11 version 22H3	10.0.22631.0 to < 10.0.22631.6649	Vulnerable
Microsoft	Windows 11 Version 23H2	10.0.22631.0 to < 10.0.22631.6649	Vulnerable
Microsoft	Windows 11 Version 24H2	10.0.26100.0 to < 10.0.26100.7840	Vulnerable
Microsoft	Windows 11 Version 25H2	10.0.26200.0 to < 10.0.26200.7840	Vulnerable
Microsoft	Windows 11 version 26H1	10.0.28000.0 to < 10.0.28000.1575	Vulnerable
Microsoft	Windows 11 Version 26H1	10.0.28000.0 to < 10.0.28000.1575	Vulnerable
Microsoft	Windows Server 2012	6.2.9200.0 to < 6.2.9200.25923	Vulnerable
Microsoft	Windows Server 2012 (Server Core installation)	6.2.9200.0 to < 6.2.9200.25923	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

Required

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
8.8	CVSS 3.1	high	2.8	5.9	Microsoft (CNA)
8.8	CVSS 3.1	high	—	—	Microsoft (CNA)

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-693 · Protection Mechanism Failure

Bypass Protection Mechanism::

Weakness & attack patterns

CWE-693

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-480 · Escaping VirtualizationCAPEC-237 · Escaping a Sandbox by Calling Signed Code in Another LanguageCAPEC-22 · Exploiting Trust in ClientCAPEC-20 · Encryption Brute ForcingCAPEC-36 · Using Unpublished InterfacesCAPEC-17 · Using Malicious FilesCAPEC-127 · Directory IndexingCAPEC-1 · Accessing Functionality Not Properly Constrained by ACLsCAPEC-107 · Cross Site TracingCAPEC-74 · Manipulating StateCAPEC-477 · Signature Spoofing by Mixing Signed and Unsigned ContentCAPEC-65 · Sniff Application Code

T1574.010Hijack Execution Flow: ServicesFile Permissions Weakness
T1083File and Directory Discovery
T1574.005Hijack Execution Flow: Executable Installer File Permissions Weakness

CISA KEV details

CISA lists a CVE here once it has evidence of exploitation against real targets.

CISAThat month →

Listed

Feb 10, 2026

Federal deadline

Mar 3, 2026

passed 199 days ago

Ransomware use

Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a date to argue against.

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

1 of the 3 sampled are weaponized

Exploit entries

Exploit-DB and CTI exploit indexes

Social mentions

Posts naming this CVE. Attention, not evidence of exploitation — it spikes on disclosure and decays whether or not anything is exploited.

35 more posts on this CVEShowing 5 of 40 · Who is discussing this CVE, and how loudlyUnlock free

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2, Windows 10 Version 22H2, Windows 11 version 22H3, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows 11 Version 26H1, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server 2022, 23H2 Edition (Server Core installation), Windows Server 2025, Windows Server 2025 (Server Core installation).
Monitor for scanner or exploit-pattern traffic after 5 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Groups associated with this CVE

Groups reported in connection with this vulnerability. A reported association, not a confirmed observation of that group using it — and not scoped to any sector or campaign.

Nomad Panda

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 8.8 (AV:N)
Jun 17, 2026 · NVD
Cve is exploited EpSiLoNPoInTOrI/EpSiLoNPoInTlnk
May 10, 2026 · SOCRadar CTI
Added to CISA KEV catalog
Feb 10, 2026 · CISA
Initial · CVE published
Feb 10, 2026 · NVD

Source activity

Readings a source repeats on a schedule, counted rather than listed.

29×SVRS was changedMay 12, 2026 – Jul 5, 2026 · SOCRadar CTI
8×TweetsMay 14, 2026 – Jun 16, 2026 · SOCRadar CTI
1×Github_Repos · Github repository created, EpSiLoNPoInTOrI/EpSiLoNPoInTlnkMay 9, 2026 · SOCRadar CTI

References

3 on the record

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21510
Vendor Advisory, NIST, Mitre
www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21510
US Government Resource
nvd.nist.gov/vuln/detail/CVE-2026-21510
Vendor Advisory

Coverage

18 stories from the feeds we poll

13 more reports on this CVEShowing 5 of 18 · Vendor research and security press coverageUnlock free

Elsewhere on this site

Microsoftevery CVE for this vendor
February 2026what else CISA listed
Unclassifiedsame class
CWE-693other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-21510 is Windows Shell Security Feature Bypass Vulnerability, a high vulnerability affecting Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2, Windows 10 Version 22H2, Windows 11 version 22H3, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows 11 Version 26H1, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server 2022, 23H2 Edition (Server Core installation), Windows Server 2025, Windows Server 2025 (Server Core installation) from Microsoft. The current evidence lists it in CISA KEV, and the exploit status is: Yes: CISA KEV signal present. Public exploit evidence is: 5 public PoC repositories reported; 1 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 8.8 describes technical severity, while EPSS 26% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.