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Response snapshot Oct 27, 2026, 04:12 UTC

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Advisoryproject-zero-gphfh-deep-dive-70e01b76e84c

A Deep Dive into the GetProcessHandleFromHwnd API

In my previous blog post I mentioned the GetProcessHandleFromHwnd API. This was an API I didn’t know existed until I found a publicly disclosed UAC bypass using the Quick Assist UI Access application. This API looked interesting so I thought I should take a closer look.

At a glance

Sources
1 source

What to do

Read the exact official research article before applying its defensive techniques or drawing conclusions.

Read Google Project Zero Research: A Deep Dive into the GetProcessHandleFromHwnd API (opens a new tab)

What happened

In my previous blog post I mentioned the GetProcessHandleFromHwnd API. This was an API I didn’t know existed until I found a publicly disclosed UAC bypass using the Quick Assist UI Access application. This API looked interesting so I thought I should take a closer look. I typically start by reading the documentation for an API I don’t know about, assuming it’s documented at all.

It can give you an idea of how long the API has existed as well as its security properties. The documentation’s remarks contain the following three statements that I thought were interesting: If the caller has UIAccess, however, they can use a windows hook to inject code into the target process, and from within the target process, send a handle back to the caller.

GetProcessHandleFromHwnd is a convenience function that uses this technique to obtain the handle of the process that owns the specified HWND. Note that it only succeeds in cases where the caller and target process are running as the same user.

Sources

  1. Primary source

    Google Project Zero Research: A Deep Dive into the GetProcessHandleFromHwnd API (opens a new tab)

    Exact official article/advisory identified by the feed; title, source dates, and any supplied article excerpt.

    Published Checked

  2. Primary source

    Google Project Zero Research syndication feed (opens a new tab)

    The RSS/Atom/RDF entry supplied this exact link and any available title, date, and excerpt.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, February 26). A Deep Dive into the GetProcessHandleFromHwnd API. https://kevwire.com/record/project-zero-gphfh-deep-dive-70e01b76e84c

MLA

"A Deep Dive into the GetProcessHandleFromHwnd API." KEVWire, 26 Feb. 2026, kevwire.com/record/project-zero-gphfh-deep-dive-70e01b76e84c.

Chicago

KEVWire. "A Deep Dive into the GetProcessHandleFromHwnd API." Last modified February 26, 2026. https://kevwire.com/record/project-zero-gphfh-deep-dive-70e01b76e84c.

Evidence summary (plain text)

A Deep Dive into the GetProcessHandleFromHwnd API (Feb 26, 2026).
In my previous blog post I mentioned the GetProcessHandleFromHwnd API. This was an API I didn’t know existed until I found a publicly disclosed UAC bypass using the Quick Assist UI Access application. This API looked interesting so I thought I should take a closer look. I typically start by reading the documentation for an API I don’t know about, assuming it’s documented at all. It can give you an idea of how long the API has existed as well as its security properties. The documentation’s remarks contain the following three statements that I thought were interesting: If the caller has UIAccess, however, they can use a windows hook to inject code into the target process, and from within the target process, send a handle back to the caller. GetProcessHandleFromHwnd is a convenience function that uses this technique to obtain the handle of the process that owns the specified HWND. Note that it only succeeds in cases where the caller and target process are running as the same user.
Sources:
Google Project Zero Research: A Deep Dive into the GetProcessHandleFromHwnd API: https://projectzero.google/2026/02/gphfh-deep-dive.html
Google Project Zero Research syndication feed: https://projectzero.google/feed.xml
Record ID: project-zero-gphfh-deep-dive-70e01b76e84c.
Record origin: Ingested record.
AI evidence: Not assessed.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 03:35 UTC. Ingestion is not an independent editorial investigation.

This is an excerpt of official research, not a reproduced result or evidence of exposure to a scored vulnerability.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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