CVE-2026-21513
What it is
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
At a glance
- Exploitability
- Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure, data tampering, service disruption.
- In the wild
- CISA lists this as exploited in real attacks. Treat as urgent.
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- ReservedThe CVE id was reserved by its CNA
- 2026-02-10 Exploited in the wildAdded to CISA's Known Exploited Vulnerabilities list
- PublishedDisclosed publicly on CVE.org and NVD
- 2026-03-03 Remediation deadlineCISA's due date for federal agencies to fix it
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: yes, CISA lists it. This puts it above everything that is not.
- Exploit odds: 15.9% in the next 30 days (EPSS).
- Severity: 8.8 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Added to CISA KEV
- 2026-02-10
- Exploit probability
- 15.9% · EPSS, next 30 days
- Weakness
- CWE-693
- Record status
- Analyzed
Affected
- Microsoft Windows 10 1607 < 10.0.14393.8868
- Microsoft Windows 10 1809 < 10.0.17763.8389
- Microsoft Windows 10 21h2 < 10.0.19044.6937
- Microsoft Windows 10 22h2 < 10.0.19045.6937
- Microsoft Windows 11 23h2 < 10.0.22631.6649
- Microsoft Windows 11 24h2 < 10.0.26100.7781
- Microsoft Windows 11 25h2 < 10.0.26200.7781
- Microsoft Windows Server 2012
Attack profile CVSS 3.1 · 8.8
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-21513.md and follow it. Check whether this project is affected by CVE-2026-21513. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21513
- https://www.vicarius.io/vsociety/posts/cve-2026-21513-mitigation-script-security-feature-bypass-vulnerability-in-mshtml-framework
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21513
- https://www.vicarius.io/vsociety/posts/cve-2026-21513-detection-script-security-feature-bypass-vulnerability-in-mshtml-framework
- https://www.vicarius.io/vsociety/posts/cve-2026-21513-mitigation-script-security-feature-bypass-vulnerability-in-mshtml-framework
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21513