diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index fc916c470a0110..101c6042f0073f 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -509,9 +509,12 @@ def _default_mime_types():
         '.m3u8'   : 'application/vnd.apple.mpegurl',
         '.dll'    : 'application/vnd.microsoft.portable-executable',
         '.exe'    : 'application/vnd.microsoft.portable-executable',
+        '.cab'    : 'application/vnd.ms-cab-compressed',
         '.xls'    : 'application/vnd.ms-excel',
         '.xlb'    : 'application/vnd.ms-excel',
         '.eot'    : 'application/vnd.ms-fontobject',
+        '.chm'    : 'application/vnd.ms-htmlhelp',
+        '.thmx'   : 'application/vnd.ms-officetheme',
         '.ppt'    : 'application/vnd.ms-powerpoint',
         '.pot'    : 'application/vnd.ms-powerpoint',
         '.ppa'    : 'application/vnd.ms-powerpoint',
diff --git a/Misc/NEWS.d/next/Library/2026-03-10-01-48-12.gh-issue-145717.dPc0Rt.rst b/Misc/NEWS.d/next/Library/2026-03-10-01-48-12.gh-issue-145717.dPc0Rt.rst
new file mode 100644
index 00000000000000..55ef5206c992cd
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-10-01-48-12.gh-issue-145717.dPc0Rt.rst
@@ -0,0 +1 @@
+Add a few Microsoft-specific MIME types.