diff --git a/.github/workflows/xcat_test.yml b/.github/workflows/xcat_test.yml
index cec518716..5ed312bd5 100644
--- a/.github/workflows/xcat_test.yml
+++ b/.github/workflows/xcat_test.yml
@@ -28,7 +28,8 @@ jobs:
           set -o pipefail
           docker run --rm -v "$PWD:/src:ro" -w /src fedora:42 bash -ec '
             dnf -y -q install mock perl perl-File-Slurper >/dev/null
-            prove -v xCAT-test/native/mock_resultdir_owner.t' 2>&1 | tee mock.tap
+            prove -v xCAT-test/native/mock_resultdir_owner.t \
+              xCAT-test/native/build_sources_other_uid.t' 2>&1 | tee mock.tap
           if grep -iE '# skip' mock.tap; then
             echo 'a mock result directory test was skipped' >&2
             exit 1
diff --git a/xCAT-test/native/README.md b/xCAT-test/native/README.md
index 9e0816eb8..eb1072c6e 100644
--- a/xCAT-test/native/README.md
+++ b/xCAT-test/native/README.md
@@ -39,10 +39,12 @@ sudo prove xCAT-test/native/ip_forwarding.t \
 ```
 
 The mock result directory case needs the mock Python library, and root for its
-ownership checks. The `xcat_test` workflow runs it as root in a Fedora container:
+ownership checks. The staged sources case needs root to read the sources as uid
+1000. The `xcat_test` workflow runs both as root in a Fedora container:
 
 ```
-sudo prove xCAT-test/native/mock_resultdir_owner.t
+sudo prove xCAT-test/native/mock_resultdir_owner.t \
+      xCAT-test/native/build_sources_other_uid.t
 ```
 
 The PostgreSQL case starts a private server with only a Unix socket. Run it as
diff --git a/xCAT-test/native/build_sources_other_uid.t b/xCAT-test/native/build_sources_other_uid.t
new file mode 100644
index 000000000..ea7f3d4c3
--- /dev/null
+++ b/xCAT-test/native/build_sources_other_uid.t
@@ -0,0 +1,50 @@
+#!/usr/bin/env perl
+# mock reads the staged sources as the uid of the target's chrootuid while buildrpms.pl
+# runs as root. A process with another uid must read them. CI runs this file as root.
+use strict;
+use warnings;
+use FindBin;
+use lib "$FindBin::Bin/../../build-utils/lib";
+use File::Path qw(make_path);
+use File::Slurper qw(read_text write_text);
+use File::Temp qw(tempdir);
+use POSIX ();
+use Test::More;
+use XCAT::BuildUtils qw(build_sources_base prepare_build_sources_dir share_build_sources_dir);
+
+plan skip_all => 'requires root to switch to another uid' if $> != 0;
+
+# Flush before the fork below, or the child repeats this file's TAP output on exit.
+$| = 1;
+
+my $checkout = tempdir(CLEANUP => 1);
+chmod 0755, $checkout or die "chmod $checkout: $!\n";
+# A root $HOME the build uid cannot enter, as on the build hosts.
+make_path("$checkout/root");
+chmod 0550, "$checkout/root" or die "chmod: $!\n";
+local $ENV{HOME} = "$checkout/root";
+
+my $umask = umask 077;
+my $dir = prepare_build_sources_dir(build_sources_base($checkout), $$, 'hosta');
+make_path("$dir/sub");
+write_text("$dir/xCAT-2.20.0.tar.gz", "payload\n");
+write_text("$dir/sub/xcat.conf", "conf\n");
+share_build_sources_dir($dir);
+umask $umask;
+
+my $pid = fork // die "fork: $!\n";
+if ($pid == 0) {
+    POSIX::setgid(1000);
+    POSIX::setuid(1000);
+    POSIX::_exit(2) if $> != 1000;
+    my $ok = eval {
+        opendir(my $dh, $dir) or die;
+        read_text("$dir/xCAT-2.20.0.tar.gz") eq "payload\n"
+            && read_text("$dir/sub/xcat.conf") eq "conf\n";
+    };
+    POSIX::_exit($ok ? 0 : 1);
+}
+waitpid($pid, 0);
+is($? >> 8, 0, 'uid 1000 lists the staging directory and reads every staged file');
+
+done_testing;
diff --git a/xCAT-test/unit/buildrpms_source_only.t b/xCAT-test/unit/buildrpms_source_only.t
index 2868f185d..b528a588e 100644
--- a/xCAT-test/unit/buildrpms_source_only.t
+++ b/xCAT-test/unit/buildrpms_source_only.t
@@ -51,6 +51,7 @@ our @STAGES;
     sub createmockconfig { push @main::STAGES, 'createmockconfig'; }
     sub prepare_mock_resultdirs { push @main::STAGES, 'prepare_mock_resultdirs'; }
     sub buildsources     { push @main::STAGES, 'buildsources'; }
+    sub share_build_sources_dir { push @main::STAGES, 'share_build_sources_dir'; }
     sub buildspkgs       { push @main::STAGES, 'buildspkgs'; }
     sub buildpkgs        { push @main::STAGES, 'buildpkgs'; }
     # buildall assigns a staging directory per build process.
@@ -129,11 +130,11 @@ sub stages_for {
 }
 
 is_deeply( stages_for(0),
-    [qw(createmockconfig prepare_mock_resultdirs buildsources buildspkgs buildpkgs)],
+    [qw(createmockconfig prepare_mock_resultdirs buildsources share_build_sources_dir buildspkgs buildpkgs)],
     'a normal run builds the source rpm and then rebuilds it into binaries' );
 
 is_deeply( stages_for(1),
-    [qw(createmockconfig prepare_mock_resultdirs buildsources buildspkgs)],
+    [qw(createmockconfig prepare_mock_resultdirs buildsources share_build_sources_dir buildspkgs)],
     'a source-only run stops once the source rpm exists' );
 
 ok( !grep( { $_ eq 'buildpkgs' } @{ stages_for(1) } ),
diff --git a/xCAT-test/unit/buildrpms_sources_per_package.t b/xCAT-test/unit/buildrpms_sources_per_package.t
index 0a97d9380..a55a97efa 100644
--- a/xCAT-test/unit/buildrpms_sources_per_package.t
+++ b/xCAT-test/unit/buildrpms_sources_per_package.t
@@ -4,6 +4,7 @@
 use strict;
 use warnings;
 
+use Cwd ();
 use File::Path qw(make_path);
 use File::Slurper qw(write_text);
 use File::Temp qw(tempdir);
@@ -12,11 +13,23 @@ use lib "$FindBin::Bin/../../build-utils/lib";
 use Test::More;
 
 use XCAT::BuildUtils qw(build_sources_base build_sources_dir prepare_build_sources_dir
-    remove_build_sources_dir sweep_build_sources_dirs);
+    remove_build_sources_dir sweep_build_sources_dirs share_build_sources_dir);
 
+# mock reads the staged sources as the uid of the target's chrootuid, and $HOME of a
+# root build is /root, mode 0550. The base belongs to the checkout, not to $HOME.
 my $home = tempdir(CLEANUP => 1);
+local $ENV{HOME} = "$home/home";
 my $base = build_sources_base($home);
-is($base, "$home/rpmbuild/sources", 'the base directory is under the rpmbuild tree');
+is($base, "$home/dist/sources", 'the base directory is under the dist tree of the checkout');
+unlike($base, qr{^\Q$ENV{HOME}\E/}, 'the base directory is not under $HOME');
+{
+    my $cwd = Cwd::getcwd();
+    chdir $home or die "chdir $home: $!\n";
+    my $default = build_sources_base();
+    chdir $cwd or die "chdir $cwd: $!\n";
+    is($default, Cwd::abs_path($home) . "/dist/sources",
+        'the base directory defaults to the dist tree of the working directory');
+}
 
 # Two live processes on one host never have the same pid. The host name keeps two
 # hosts apart when $HOME is on NFS.
@@ -89,4 +102,23 @@ ok(!-e $reaped, 'the default check deletes the directory of a reaped process');
 is_deeply([sweep_build_sources_dirs("$home/absent", 'hosta', $is_alive)], [],
     'a missing base directory is not an error');
 
+# Another uid must traverse every directory and read every file, whatever the umask.
+{
+    my $root  = tempdir(CLEANUP => 1);
+    my $umask = umask 077;
+    my $sbase = build_sources_base($root);
+    my $dir   = prepare_build_sources_dir($sbase, 401, 'hosta');
+    make_path("$dir/sub");
+    write_text("$dir/xCAT-2.20.0.tar.gz", "payload\n");
+    write_text("$dir/sub/xcat.conf", "conf\n");
+    share_build_sources_dir($dir);
+    umask $umask;
+    for my $d ("$root/dist", $sbase, $dir, "$dir/sub") {
+        is((stat $d)[2] & 0055, 0055, "other users can list and enter $d");
+    }
+    for my $f ("$dir/xCAT-2.20.0.tar.gz", "$dir/sub/xcat.conf") {
+        is((stat $f)[2] & 0044, 0044, "other users can read $f");
+    }
+}
+
 done_testing;