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Security fix for CVE-2026-21441

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Related: RHEL-139410
This commit is contained in:
Miro Hrončok 2026-01-12 12:35:16 +01:00
parent 5555a0d7f0
commit b043dfbce0
2 changed files with 222 additions and 0 deletions
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219
CVE-2026-21441.patch Normal file
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@ -0,0 +1,219 @@
From 5474aa5a56209bf0378201d8305584a0f51f91c7 Mon Sep 17 00:00:00 2001
From: Ousret <ahmed.tahri@cloudnursery.dev>
Date: Thu, 17 Nov 2022 01:40:19 +0100
Subject: [PATCH 1/2] Prevent issue in HTTPResponse().read() when
decoded_content is True and then False Provided it has initialized eligible
decoder(decompressor) and did decode once
(cherry picked from commit cefd1dbba6a20ea4f017e6e472f9ada3a8a743e0)
---
changelog/2800.bugfix.rst | 1 +
src/urllib3/response.py | 13 +++++++++++++
test/test_response.py | 35 +++++++++++++++++++++++++++++++++++
3 files changed, 49 insertions(+)
create mode 100644 changelog/2800.bugfix.rst
diff --git a/changelog/2800.bugfix.rst b/changelog/2800.bugfix.rst
new file mode 100644
index 00000000..9dcf1eec
--- /dev/null
+++ b/changelog/2800.bugfix.rst
@@ -0,0 +1 @@
+Prevented issue in HTTPResponse().read() when decoded_content is True and then False.
\ No newline at end of file
diff --git a/src/urllib3/response.py b/src/urllib3/response.py
index ba366eef..6c8823be 100644
--- a/src/urllib3/response.py
+++ b/src/urllib3/response.py
@@ -331,6 +331,7 @@ class HTTPResponse(io.IOBase):
self.reason = reason
self.strict = strict
self.decode_content = decode_content
+ self._has_decoded_content = False
self.retries = retries
self.enforce_content_length = enforce_content_length
@@ -481,12 +482,19 @@ class HTTPResponse(io.IOBase):
"""
Decode the data passed in and potentially flush the decoder.
"""
+ if not decode_content and self._has_decoded_content:
+ raise RuntimeError(
+ "Calling read(decode_content=False) is not supported after "
+ "read(decode_content=True) was called."
+ )
+
if max_length is None or flush_decoder:
max_length = -1
try:
if decode_content and self._decoder:
data = self._decoder.decompress(data, max_length=max_length)
+ self._has_decoded_content = True
except (IOError, zlib.error) as e:
content_encoding = self.headers.get('content-encoding', '').lower()
raise DecodeError(
@@ -670,6 +678,11 @@ class HTTPResponse(io.IOBase):
else:
# do not waste memory on buffer when not decoding
if not decode_content:
+ if self._has_decoded_content:
+ raise RuntimeError(
+ "Calling read(decode_content=False) is not supported after "
+ "read(decode_content=True) was called."
+ )
return data
decoded_data = self._decode(
diff --git a/test/test_response.py b/test/test_response.py
index bd083b7f..4b04e409 100644
--- a/test/test_response.py
+++ b/test/test_response.py
@@ -560,6 +560,41 @@ class TestResponse(object):
while not br.closed:
br.read(5)
+ def test_read_with_illegal_mix_decode_toggle(self):
+ compress = zlib.compressobj(6, zlib.DEFLATED, -zlib.MAX_WBITS)
+ data = compress.compress(b"foo")
+ data += compress.flush()
+
+ fp = BytesIO(data)
+
+ resp = HTTPResponse(
+ fp, headers={"content-encoding": "deflate"}, preload_content=False
+ )
+
+ assert resp.read(1) == b"f"
+
+ with pytest.raises(
+ RuntimeError,
+ match=(
+ r"Calling read\(decode_content=False\) is not supported after "
+ r"read\(decode_content=True\) was called"
+ ),
+ ):
+ resp.read(1, decode_content=False)
+
+ def test_read_with_mix_decode_toggle(self):
+ compress = zlib.compressobj(6, zlib.DEFLATED, -zlib.MAX_WBITS)
+ data = compress.compress(b"foo")
+ data += compress.flush()
+
+ fp = BytesIO(data)
+
+ resp = HTTPResponse(
+ fp, headers={"content-encoding": "deflate"}, preload_content=False
+ )
+ resp.read(1, decode_content=False)
+ assert resp.read(1, decode_content=True) == b"o"
+
def test_streaming(self):
fp = BytesIO(b'foo')
resp = HTTPResponse(fp, preload_content=False)
--
2.52.0
From 018e71279b1b9ba9319943dbe47762d2dad631d0 Mon Sep 17 00:00:00 2001
From: Illia Volochii <illia.volochii@gmail.com>
Date: Wed, 7 Jan 2026 18:07:30 +0200
Subject: [PATCH 2/2] Security fix for CVE-2026-21441
* Stop decoding response content during redirects needlessly
* Rename the new query parameter
* Add a changelog entry
(cherry picked from commit 8864ac407bba8607950025e0979c4c69bc7abc7b)
---
CHANGES.rst | 3 +++
dummyserver/handlers.py | 8 +++++++-
src/urllib3/connectionpool.py | 6 +++++-
test/with_dummyserver/test_connectionpool.py | 19 +++++++++++++++++++
4 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/CHANGES.rst b/CHANGES.rst
index cf315aaf..5673a58e 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -8,6 +8,9 @@ Backports
compressed HTTP content ("decompression bombs") leading to excessive resource
consumption even when a small amount of data was requested. Reading small
chunks of compressed data is safer and much more efficient now.
+- Fixed a high-severity security issue where decompression-bomb safeguards of
+ the streaming API were bypassed when HTTP redirects were followed.
+ (`GHSA-38jv-5279-wg99 <https://github.com/urllib3/urllib3/security/advisories/GHSA-38jv-5279-wg99>`__)
1.24.2 (2019-04-17)
diff --git a/dummyserver/handlers.py b/dummyserver/handlers.py
index f570d881..c0dd4e4a 100644
--- a/dummyserver/handlers.py
+++ b/dummyserver/handlers.py
@@ -170,9 +170,15 @@ class TestingApp(RequestHandler):
status = request.params.get('status', '303 See Other')
if len(status) == 3:
status = '%s Redirect' % status.decode('latin-1')
+ compressed = request.params.get('compressed') == b'true'
headers = [('Location', target)]
- return Response(status=status, headers=headers)
+ if compressed:
+ headers.append(('Content-Encoding', 'gzip'))
+ data = gzip.compress(b'foo')
+ else:
+ data = b''
+ return Response(data, status=status, headers=headers)
def not_found(self, request):
return Response('Not found', status='404 Not Found')
diff --git a/src/urllib3/connectionpool.py b/src/urllib3/connectionpool.py
index ad6303c1..5f66cd25 100644
--- a/src/urllib3/connectionpool.py
+++ b/src/urllib3/connectionpool.py
@@ -671,7 +671,11 @@ class HTTPConnectionPool(ConnectionPool, RequestMethods):
try:
# discard any remaining response body, the connection will be
# released back to the pool once the entire response is read
- response.read()
+ response.read(
+ # Do not spend resources decoding the content unless
+ # decoding has already been initiated.
+ decode_content=response._has_decoded_content,
+ )
except (TimeoutError, HTTPException, SocketError, ProtocolError,
BaseSSLError, SSLError) as e:
pass
diff --git a/test/with_dummyserver/test_connectionpool.py b/test/with_dummyserver/test_connectionpool.py
index 5faa0638..a2673e05 100644
--- a/test/with_dummyserver/test_connectionpool.py
+++ b/test/with_dummyserver/test_connectionpool.py
@@ -413,6 +413,25 @@ class TestConnectionPool(HTTPDummyServerTestCase):
self.assertEqual(r.status, 200)
self.assertEqual(r.data, b'Dummy server!')
+ @mock.patch("urllib3.response.GzipDecoder.decompress")
+ def test_no_decoding_with_redirect_when_preload_disabled(
+ self, gzip_decompress
+ ):
+ """
+ Test that urllib3 does not attempt to decode a gzipped redirect
+ response when `preload_content` is set to `False`.
+ """
+ with HTTPConnectionPool(self.host, self.port) as pool:
+ # Three requests are expected: two redirects and one final / 200 OK.
+ response = pool.request(
+ "GET",
+ "/redirect",
+ fields={"target": "/redirect?compressed=true", "compressed": "true"},
+ preload_content=False,
+ )
+ assert response.status == 200
+ gzip_decompress.assert_not_called()
+
def test_bad_connect(self):
pool = HTTPConnectionPool('badhost.invalid', self.port)
try:
--
2.52.0

3
python-urllib3.spec
View File

@ -57,6 +57,7 @@ Patch6: CVE-2024-37891.patch
Patch7: CVE-2025-66471.patch
Patch8: CVE-2025-66418.patch
Patch9: CVE-2026-21441.patch
%description
Python HTTP module with connection pooling and file POST abilities.
@ -92,6 +93,7 @@ Python3 HTTP module with connection pooling and file POST abilities.
%patch6 -p1
%patch7 -p1
%patch8 -p1
%patch9 -p1
# Make sure that the RECENT_DATE value doesn't get too far behind what the current date is.
# RECENT_DATE must not be older that 2 years from the build time, or else test_recent_date
@ -170,6 +172,7 @@ popd
* Wed Dec 17 2025 Miro Hrončok <mhroncok@redhat.com> - 1.24.2-9
- Security fix for CVE-2025-66471
- Security fix for CVE-2025-66418
- Security fix for CVE-2026-21441
Resolves: RHEL-139410
* Mon Jul 01 2024 Lumír Balhar <lbalhar@redhat.com> - 1.24.2-8