CVE-2020-27619: Insufficient Information (NVD-CWE-noinfo)
value: In Python 3 through 3.9.0, the Lib/test/multibytecodec_support.py CJK codec tests call eval() on content retrieved via HTTP.
CWE description: There is insufficient information about the issue to classify it; details are unkown or unspecified.
CVSS v3 base score: 9.8
Published: 2020-10-22T03:16Z
Repository: https://github.com/python/cpython
Language: Other
Files changed: Lib/test/multibytecodec_support.py, Misc/NEWS.d/next/Tests/2020-10-05-17-43-46.bpo-41944.rf1dYb.rst
Commit date: 2020-10-06 15:14:51 +0300
Commit message: bpo-41944: No longer call eval() on content received via HTTP in the CJK codec tests (GH-22566)


Diff: diff --git a/Lib/test/multibytecodec_support.py b/Lib/test/multibytecodec_support.py
index cca8af67d6d..f76c0153f5e 100644
--- a/Lib/test/multibytecodec_support.py
+++ b/Lib/test/multibytecodec_support.py
@@ -303,33 +303,27 @@ def test_mapping_file(self):
             self._test_mapping_file_ucm()
         else:
             self._test_mapping_file_plain()
 
     def _test_mapping_file_plain(self):
-        unichrs = lambda s: ''.join(map(chr, map(eval, s.split('+'))))
+        def unichrs(s):
+            return ''.join(chr(int(x, 16)) for x in s.split('+'))
+
         urt_wa = {}
 
         with self.open_mapping_file() as f:
             for line in f:
                 if not line:
                     break
-                data = line.split('#')[0].strip().split()
+                data = line.split('#')[0].split()
                 if len(data) != 2:
                     continue
 
-                csetval = eval(data[0])
-                if csetval <= 0x7F:
-                    csetch = bytes([csetval & 0xff])
-                elif csetval >= 0x1000000:
-                    csetch = bytes([(csetval >> 24), ((csetval >> 16) & 0xff),
-                                    ((csetval >> 8) & 0xff), (csetval & 0xff)])
-                elif csetval >= 0x10000:
-                    csetch = bytes([(csetval >> 16), ((csetval >> 8) & 0xff),
-                                    (csetval & 0xff)])
-                elif csetval >= 0x100:
-                    csetch = bytes([(csetval >> 8), (csetval & 0xff)])
-                else:
+                if data[0][:2] != '0x':
+                    self.fail(f"Invalid line: {line!r}")
+                csetch = bytes.fromhex(data[0][2:])
+                if len(csetch) == 1 and 0x80 <= csetch[0]:
                     continue
 
                 unich = unichrs(data[1])
                 if ord(unich) == 0xfffd or unich in urt_wa:
                     continue
diff --git a/Misc/NEWS.d/next/Tests/2020-10-05-17-43-46.bpo-41944.rf1dYb.rst b/Misc/NEWS.d/next/Tests/2020-10-05-17-43-46.bpo-41944.rf1dYb.rst
new file mode 100644
index 00000000000..4f9782f1c85
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2020-10-05-17-43-46.bpo-41944.rf1dYb.rst
@@ -0,0 +1 @@
+Tests for CJK codecs no longer call ``eval()`` on content received via HTTP.

Vulnerable code:         unichrs = lambda s: ''.join(map(chr, map(eval, s.split('+'))))
                data = line.split('#')[0].strip().split()
                csetval = eval(data[0])
                if csetval <= 0x7F:
                    csetch = bytes([csetval & 0xff])
                elif csetval >= 0x1000000:
                    csetch = bytes([(csetval >> 24), ((csetval >> 16) & 0xff),
                                    ((csetval >> 8) & 0xff), (csetval & 0xff)])
                elif csetval >= 0x10000:
                    csetch = bytes([(csetval >> 16), ((csetval >> 8) & 0xff),
                                    (csetval & 0xff)])
                elif csetval >= 0x100:
                    csetch = bytes([(csetval >> 8), (csetval & 0xff)])
                else:
Fixed code:         def unichrs(s):
            return ''.join(chr(int(x, 16)) for x in s.split('+'))

                data = line.split('#')[0].split()
                if data[0][:2] != '0x':
                    self.fail(f"Invalid line: {line!r}")
                csetch = bytes.fromhex(data[0][2:])
                if len(csetch) == 1 and 0x80 <= csetch[0]:
Tests for CJK codecs no longer call ``eval()`` on content received via HTTP.