gh-158494: zipimport: raise ZipImportError for corrupt deflate data

Author: Tony123-tech

Lib/test/test_zipimport.py

@@ -1021,6 +1021,29 @@ def assertDataEntry(name):
 class DeflateCompressedZipImportTestCase(UncompressedZipImportTestCase):
     compression = ZIP_DEFLATED
 
+    def testCorruptDeflateDataRaisesZipImportError(self):
+        # gh-158494: a corrupt deflate stream in a .pyc must surface as.
+        # ZipImportError, not zlib.error.
+        files = {TESTMOD + pyc_ext: test_pyc}
+        self.makeZip(files)
+
+        # Corrupt the deflate stream of the .pyc entry in place.
+        with open(TEMP_ZIP, "r+b") as f:
+            data = f.read()
+            idx = data.find((TESTMOD + pyc_ext).encode())
+            lh = data.rfind(b"PK\x03\x04")
+            name_len, extra_len = struct.unpack_from("<HH", data, lh + 26)
+            data_start = lh + 30 + name_len + extra_len
+            f.seek(data_start)
+            f.write(b"\xff" * 8)
+
+        zipimport._zip_directory_cache.clear()
+        sys.path.insert(0, TEMP_ZIP)
+        self.addCleanup(sys.modules.pop, TESTMOD, None)
+        importlib.invalidate_caches()
+
+        with self.assertRaises(zipimport.ZipImportError):
+            importlib.import_module(TESTMOD)
 
 @support.requires_zstd()
 class ZStdCompressedZipImportTestCase(UncompressedZipImportTestCase):

Lib/zipimport.py

@@ -668,7 +668,10 @@ def _get_data(archive, toc_entry):
                 decompress = _get_zlib_decompress_func()
             except Exception:
                 raise ZipImportError("can't decompress data; zlib not available")
-            return decompress(raw_data, -15)
+            try:
+                return decompress(raw_data, -15)
+            except Exception:
+                raise ZipImportError("could not decompress deflate data")
         case 93:  # zstd
             try:
                 return _zstd_decompress(raw_data)

Misc/NEWS.d/next/Library/2026-09-30-19-30-00.gh-issue-158494.AbCdEf.rst

@@ -0,0 +1,2 @@
+Fix :mod:`zipimport` to raise :exc:`zipimport.ZipImportError` instead of
+leaking :exc:`zlib.error` when a zip entry's deflate stream is corrupt.