https://github.com/python/cpython/commit/b062727097e997bcb900e11503d3248daac903da
commit: b062727097e997bcb900e11503d3248daac903da
branch: main
author: Stan Ulbrych <[email protected]>
committer: StanFromIreland <[email protected]>
date: 2026-08-22T19:45:59+01:00
summary:
gh-156180: Reject a negative `len2` in `zlib.{adler32,crc32}_combine()`
(#156181)
Co-authored-by: Bénédikt Tran <[email protected]>
files:
A Misc/NEWS.d/next/Library/2026-08-21-14-30-00.gh-issue-156180.Qz3Lv8.rst
M .github/CODEOWNERS
M Lib/test/test_zlib.py
M Modules/zlibmodule.c
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 247b84ba37bbbd4..5cff59e83dd1dd4 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -620,6 +620,12 @@ Lib/test/test_unittest/testmock/ @cjw296
# Weakref
**/*weakref* @kumaraditya303
+# Zlib
+Doc/library/zlib.rst @StanFromIreland
+Lib/compression/zlib.py @StanFromIreland
+Lib/test/test_zlib.py @StanFromIreland
+Modules/_zlibmodule.c @StanFromIreland
+
# Zipfile.Path
Lib/test/test_zipfile/_path/ @jaraco
Lib/zipfile/_path/ @jaraco
diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
index 46c84c55c93398d..70d1cd81ac6c46d 100644
--- a/Lib/test/test_zlib.py
+++ b/Lib/test/test_zlib.py
@@ -182,6 +182,9 @@ def test_combine_no_iv_invalid_length(self):
self.assertNotEqual(invalid_res, checksum)
self.assertRaises(TypeError, self.combine, 0, 0, "len")
+ self.assertRaises(ValueError, self.combine, 0, 0, -1)
+ self.assertRaises(OverflowError, self.combine, 0, 0, 2**1000)
+ self.assertRaises(OverflowError, self.combine, 0, 0, -2**1000)
def test_combine_with_iv(self):
for _ in range(self.N):
diff --git
a/Misc/NEWS.d/next/Library/2026-08-21-14-30-00.gh-issue-156180.Qz3Lv8.rst
b/Misc/NEWS.d/next/Library/2026-08-21-14-30-00.gh-issue-156180.Qz3Lv8.rst
new file mode 100644
index 000000000000000..5730627e49e98fb
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-21-14-30-00.gh-issue-156180.Qz3Lv8.rst
@@ -0,0 +1,3 @@
+:func:`zlib.adler32_combine` and :func:`zlib.crc32_combine` now raise
+:exc:`ValueError` if the *len2* argument is negative, instead of returning
+rubbish or hanging indefinitely, respectively.
diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index 0a6732835eb51f5..d06b94d1e83713c 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -1948,7 +1948,10 @@ zlib_adler32_combine_impl(PyObject *module, unsigned int
adler1,
#else
z_off_t len = convert_to_z_off_t(len2);
#endif
- if (PyErr_Occurred()) {
+ if (len < 0) {
+ if (!PyErr_Occurred()) {
+ PyErr_SetString(PyExc_ValueError, "len2 must be non-negative");
+ }
return (unsigned int)-1;
}
return adler32_combine(adler1, adler2, len);
@@ -2033,7 +2036,10 @@ zlib_crc32_combine_impl(PyObject *module, unsigned int
crc1,
#else
z_off_t len = convert_to_z_off_t(len2);
#endif
- if (PyErr_Occurred()) {
+ if (len < 0) {
+ if (!PyErr_Occurred()) {
+ PyErr_SetString(PyExc_ValueError, "len2 must be non-negative");
+ }
return (unsigned int)-1;
}
return crc32_combine(crc1, crc2, len);
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