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Fix for partial PowerShell module search paths, that can be resolved to CWD locations - #17231

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Ilya (iSazonov) merged 1 commit into
PowerShell:masterfrom
anmenaga:cwd_locations_fix
May 1, 2022
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Fix for partial PowerShell module search paths, that can be resolved to CWD locations#17231
Ilya (iSazonov) merged 1 commit into
PowerShell:masterfrom
anmenaga:cwd_locations_fix

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@anmenaga Andrew (anmenaga) commented Apr 29, 2022

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PR Summary

Cherry picked from release branch.

PR Checklist

@TravisEz13 unknown
Merged PR 20126: Fix for partial PowerShell module search paths, that…
348db98 
… can be resolved to CWD locations

The problem is .NET will return empty strings for special folders that don't exist in some accounts (like System account), and the module path code appends path locations without first checking if the root path is non-empty.  This results in partial paths in the PSModulePath list, which are then interpreted by .NET file APIs as rooted in the current working directory.  And this in turn can allow low privilege users to drop modules in locations that higher privilege accounts will load from, thus gaining escalated privilege code execution.

These changes detect this non-rooted condition and prevents partial paths from being included in search lists.

Cherry picked from !17201
@ghost ghost assigned Ilya (iSazonov) Apr 29, 2022
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This PR has 33 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

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Label      : Extra Small
Size       : +26 -7
Percentile : 13.2%

Total files changed: 3

Change summary by file extension:
.cs : +23 -7
.resx : +3 -0

Change counts above are quantified counts, based on the PullRequestQuantifier customizations.

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@iSazonov
Ilya (iSazonov) merged commit c3b7e10 into PowerShell:master May 1, 2022
@TravisEz13 Travis Plunk (TravisEz13) added the CL-Engine Indicates that a PR should be marked as an engine change in the Change Log label May 5, 2022
@ghost

Deleted user (ghost) commented May 23, 2022

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🎉v7.3.0-preview.4 has been released which incorporates this pull request.:tada:

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Thatgfsj (Thatgfsj) pushed a commit to Thatgfsj/PowerShell that referenced this pull request Aug 6, 2026
Andrew @TravisEz13
Merged PR 20126: Fix for partial PowerShell module search paths, that…
ff5f212 
… can be resolved to CWD locations (PowerShell#17231)

The problem is .NET will return empty strings for special folders that don't exist in some accounts (like System account), and the module path code appends path locations without first checking if the root path is non-empty.  This results in partial paths in the PSModulePath list, which are then interpreted by .NET file APIs as rooted in the current working directory.  And this in turn can allow low privilege users to drop modules in locations that higher privilege accounts will load from, thus gaining escalated privilege code execution.

These changes detect this non-rooted condition and prevents partial paths from being included in search lists.

Cherry picked from !17201

Co-authored-by: Travis Plunk <tplunk@microsoft.com>
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@TravisEz13 Travis Plunk (TravisEz13) TravisEz13 approved these changes
@daxian-dbw Dongbo Wang (daxian-dbw) Awaiting requested review from daxian-dbw
@SteveL-MSFT Steve Lee (SteveL-MSFT) Awaiting requested review from SteveL-MSFT

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@iSazonov Ilya (iSazonov)

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@anmenaga @TravisEz13 @iSazonov