When an Expat parser with a registered ElementDeclHandler parses an inline
document type definition containing a deeply nested content model a C stack
overflow occurs.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
References 7
https://github.com/python/cpython/commit/196edfb06a7458377d4d0f4b3cd41724c1f3bd…
cna@python.org
https://github.com/python/cpython/commit/e0a8a6da90597a924b300debe045cdb4628ee1…
cna@python.org
https://github.com/python/cpython/commit/eb0e8be3a7e11b87d198a2c3af1ed0eccf5327…
cna@python.org
https://github.com/python/cpython/issues/145986
cna@python.org
https://github.com/python/cpython/pull/145987
cna@python.org
https://mail.python.org/archives/list/security-announce@python.org/thread/5M7CG…
cna@python.org
http://www.openwall.com/lists/oss-security/2026/03/16/4
af854a3a-2127-422b-91ae-364da2661108