Uncontrolled recursion in Python - CVE-2026-4224
Published: March 23, 2026
Vulnerability identifier: #VU124221
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-4224
CWE-ID: CWE-674
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform a denial of service attack.
The vulnerability exists due to uncontrolled recursion in conv_content_model() when parsing document type definition containing a deeply nested content model. A remote attacker can pass specially crafted input to the application and perform a denial of service attack.
Affected software
Python
How to mitigate CVE-2026-4224
Install updates from vendor's repository.
External References
- https://github.com/python/cpython/commit/196edfb06a7458377d4d0f4b3cd41724c1f3bd4a
- https://github.com/python/cpython/commit/e0a8a6da90597a924b300debe045cdb4628ee1f3
- https://github.com/python/cpython/commit/eb0e8be3a7e11b87d198a2c3af1ed0eccf532768
- https://github.com/python/cpython/issues/145986
- https://github.com/python/cpython/pull/145987
- https://mail.python.org/archives/list/security-announce@python.org/thread/5M7CGUW3XBRY7II4DK43KF7NQQ3TPZ6R/