https://github.com/python/cpython/commit/196edfb06a7458377d4d0f4b3cd41724c1f3bd4a commit: 196edfb06a7458377d4d0f4b3cd41724c1f3bd4a branch: 3.13 author: Miss Islington (bot) <[email protected]> committer: kumaraditya303 <[email protected]> date: 2026-03-16T14:39:27+05:30 summary:
[3.13] gh-145986: Avoid unbound C recursion in `conv_content_model` in `pyexpat.c` (CVE 2026-4224) (GH-145987) (#145996) * 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) Co-authored-by: Stan Ulbrych <[email protected]> Co-authored-by: Bénédikt Tran <[email protected]> * Remvoe `skip_if_unlimited_stack_size` decorator * Remove more decorators not on this branch --------- Co-authored-by: Stan Ulbrych <[email protected]> Co-authored-by: Bénédikt Tran <[email protected]> files: A Misc/NEWS.d/next/Security/2026-03-14-17-31-39.gh-issue-145986.ifSSr8.rst M Lib/test/test_pyexpat.py M Modules/pyexpat.c diff --git a/Lib/test/test_pyexpat.py b/Lib/test/test_pyexpat.py index 6f6c85755be452..cceeff4341e89d 100644 --- a/Lib/test/test_pyexpat.py +++ b/Lib/test/test_pyexpat.py @@ -688,6 +688,22 @@ def test_trigger_leak(self): parser.ElementDeclHandler = lambda _1, _2: None self.assertRaises(TypeError, parser.Parse, data, True) + 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 00000000000000..79536d1fef543f --- /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`. diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c index 06b7a10782802f..1eeff2ea91a39b 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_import.h" // _PyImport_SetModule() #include "pycore_pyhash.h" // _Py_HashSecret #include "pycore_traceback.h" // _PyTraceback_Add() @@ -572,6 +573,10 @@ 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; @@ -583,7 +588,7 @@ 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); } @@ -591,6 +596,8 @@ conv_content_model(XML_Content * const model, model->type, model->quant, conv_string,model->name, children); } +done: + _Py_LeaveRecursiveCall(); return result; } _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
