CVE-2026-21250: CVE-2026-21250: Untrusted pointer dereference in Windows HTTP.sys allows an authorized attacker to elevate…

What it is

Untrusted pointer dereference in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

Exploitation evidence

First exploit evidence seen: 2026-05-04 (earliest date across the sources below).

Exploited in the wild

No source on this site lists in-the-wild exploitation yet (CISA KEV, VulnCheck KEV).

Public exploit code

Exploit-DB

• EDB-52546: Windows 11 24H2 - Local Privilege Escalation (2026-05-04)

GitHub proof-of-concept repositories below quality bar

1 public repositories from 1 accounts, first seen 2026-05-04.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: Exploit-DB (OffSec) · nomi-sec/PoC-in-GitHub.

How to fix it

Fixed versions

• microsoft windows 11 24h2: upgrade to 10.0.26100.7781 or later
• microsoft windows 11 25h2: upgrade to 10.0.26200.7781 or later
• microsoft windows server 2022 23h2: upgrade to 10.0.25398.2149 or later
• microsoft windows server 2025: upgrade to 10.0.26100.32313 or later

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21250 (Vendor Advisory)

Detection Generic guidance

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.