Strix
26.1K

CVE-2026-21240

HIGHCVSS 7/10EPSS 0.27%

Last modified

CVE-2026-21240 is a high-severity vulnerability rated 7/10 on the CVSS scale. Time-of-check time-of-use (toctou) race condition in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.. EPSS estimates a 0.27% chance of exploitation in the next 30 days.

Description

Time-of-check time-of-use (toctou) race condition in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

Metrics

CVSS 3.1
7/10

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

EPSS Probability
0.27%

18.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
MicrosoftWindows 10 1809< 10.0.17763.8389
MicrosoftWindows 10 21h2< 10.0.19044.6937
MicrosoftWindows 10 22h2< 10.0.19045.6937
MicrosoftWindows 11 23h2< 10.0.22631.6649
MicrosoftWindows 11 24h2< 10.0.26100.7781
MicrosoftWindows 11 25h2< 10.0.26200.7781
MicrosoftWindows Server 2019< 10.0.17763.8389
MicrosoftWindows Server 2022< 10.0.20348.4711
MicrosoftWindows Server 2022 23h2< 10.0.25398.2149
MicrosoftWindows Server 2025< 10.0.26100.32313

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-21240?
Time-of-check time-of-use (toctou) race condition in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.
How severe is CVE-2026-21240?
CVE-2026-21240 has a CVSS score of 7/10 (HIGH severity). The EPSS model estimates a 0.27% probability of exploitation in the next 30 days.
How do I fix CVE-2026-21240?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-21240?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST