python3: fix CVE-2026-4224

Backport patch to fix CVE-2026-4224. https://nvd.nist.gov/vuln/detail/CVE-2026-4224 Upstream fix: https://github.com/python/cpython/commit/642865ddf4b232da1f3b1f7abcfa3254c4bfe785 Tested with ptest: Before: PASSED: 40007, FAILED: 0, SKIPPED: 1877 After: PASSED: 40006, FAILED: 0, SKIPPED: 1877 (From OE-Core rev: 736dd8c8f90d43e4bcdb0954a99764a62fccc20e) Signed-off-by: Amaury Couderc <amaury.couderc@est.tech> Signed-off-by: Yoann Congal <yoann.congal@smile.fr> Signed-off-by: Paul Barker <paul@pbarker.dev>
2026-07-16 15:57:04 +00:00 · 2026-06-26 16:28:08 +02:00
parent 2c373fb9b9
commit f47c0cb3bf
2 changed files with 122 additions and 0 deletions
@@ -0,0 +1,121 @@
+From ca301e24e20d1d9d58bbd432ff103cab2cb87128 Mon Sep 17 00:00:00 2001
+From: Stan Ulbrych <stan@python.org>
+Date: Wed, 8 Apr 2026 11:27:39 +0100
+Subject: [PATCH] gh-145986: Avoid unbound C recursion in `conv_content_model`
+ in `pyexpat.c` (CVE-2026-4224) (GH-145987) (#146000)
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+* [3.11] gh-145986: Avoid unbound C recursion in `conv_content_model` in `pyexpat.c` (CVE-2026-4224) (GH-145987)
+
+Fix C stack overflow (CVE-2026-4224) when an Expat parser
+with a registered `ElementDeclHandler` parses inline DTD
+containing deeply nested content model.
+
+---------
+(cherry picked from commit eb0e8be3a7e11b87d198a2c3af1ed0eccf532768)
+(cherry picked from commit e5caf45faac74b0ed869e3336420cffd3510ce6e)
+
+Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
+Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
+
+* Update Misc/NEWS.d/next/Security/2026-03-14-17-31-39.gh-issue-145986.ifSSr8.rst
+
+---------
+
+Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
+
+CVE: CVE-2026-4224
+Upstream-Status: Backport [https://github.com/python/cpython/commit/642865ddf4b232da1f3b1f7abcfa3254c4bfe785]
+
+Signed-off-by: Amaury Couderc <amaury.couderc@est.tech>
+---
+ Lib/test/test_pyexpat.py                       | 18 ++++++++++++++++++
+ ...6-03-14-17-31-39.gh-issue-145986.ifSSr8.rst |  4 ++++
+ Modules/pyexpat.c                              |  9 ++++++++-
+ 3 files changed, 30 insertions(+), 1 deletion(-)
+ create mode 100644 Misc/NEWS.d/next/Security/2026-03-14-17-31-39.gh-issue-145986.ifSSr8.rst
+
+diff --git a/Lib/test/test_pyexpat.py b/Lib/test/test_pyexpat.py
+index 38f951573f0..37d9086f40a 100644
+--- a/Lib/test/test_pyexpat.py
+++ b/Lib/test/test_pyexpat.py
+@@ -675,6 +675,24 @@ class ChardataBufferTest(unittest.TestCase):
+         parser.Parse(xml2, True)
+         self.assertEqual(self.n, 4)
+ 
+class ElementDeclHandlerTest(unittest.TestCase):
+    def test_deeply_nested_content_model(self):
+        # This should raise a RecursionError and not crash.
+        # See https://github.com/python/cpython/issues/145986.
+        N = 500_000
+        data = (
+            b'<!DOCTYPE root [\n<!ELEMENT root '
+            + b'(a, ' * N + b'a' + b')' * N
+            + b'>\n]>\n<root/>\n'
+        )
+
+        parser = expat.ParserCreate()
+        parser.ElementDeclHandler = lambda _1, _2: None
+        with support.infinite_recursion():
+            with self.assertRaises(RecursionError):
+                parser.Parse(data)
+
+
+ class MalformedInputTest(unittest.TestCase):
+     def test1(self):
+         xml = b"\0\r\n"
+diff --git a/Misc/NEWS.d/next/Security/2026-03-14-17-31-39.gh-issue-145986.ifSSr8.rst b/Misc/NEWS.d/next/Security/2026-03-14-17-31-39.gh-issue-145986.ifSSr8.rst
+new file mode 100644
+index 00000000000..cb9dbadb72d
+--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2026-03-14-17-31-39.gh-issue-145986.ifSSr8.rst
+@@ -0,0 +1,4 @@
+:mod:`xml.parsers.expat`: Fixed a crash caused by unbounded C recursion when
+converting deeply nested XML content models with
+:meth:`~xml.parsers.expat.xmlparser.ElementDeclHandler`.
+This addresses `CVE-2026-4224 <https://www.cve.org/CVERecord?id=CVE-2026-4224>`_.
+diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
+index 79492ca5c4f..8673540f358 100644
+--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
+@@ -3,6 +3,7 @@
+ #endif
+ 
+ #include "Python.h"
+#include "pycore_ceval.h"           // _Py_EnterRecursiveCall()
+ #include "pycore_runtime.h"         // _Py_ID()
+ #include <ctype.h>
+ 
+@@ -578,6 +579,10 @@ static PyObject *
+ conv_content_model(XML_Content * const model,
+                    PyObject *(*conv_string)(const XML_Char *))
+ {
+    if (_Py_EnterRecursiveCall(" in conv_content_model")) {
+        return NULL;
+    }
+
+     PyObject *result = NULL;
+     PyObject *children = PyTuple_New(model->numchildren);
+     int i;
+@@ -589,7 +594,7 @@ conv_content_model(XML_Content * const model,
+                                                  conv_string);
+             if (child == NULL) {
+                 Py_XDECREF(children);
+-                return NULL;
+                goto done;
+             }
+             PyTuple_SET_ITEM(children, i, child);
+         }
+@@ -597,6 +602,8 @@ conv_content_model(XML_Content * const model,
+                                model->type, model->quant,
+                                conv_string,model->name, children);
+     }
+done:
+    _Py_LeaveRecursiveCall();
+     return result;
+ }
+ 
+-- 
+2.34.1