C stack overflow in Expat ElementDeclHandler (CPython <3.15)
CVE-2026-4224 Published on March 16, 2026
Stack overflow parsing XML with deeply nested DTD content models
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.
Vulnerability Analysis
CVE-2026-4224 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
What is a Stack Exhaustion Vulnerability?
The product does not properly control the amount of recursion which takes place, consuming excessive resources, such as allocated memory or the program stack.
CVE-2026-4224 has been classified to as a Stack Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-4224
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Affected Versions
Python Software Foundation CPython:- Before 3.13.13 is affected.
- Version 3.14.0 and below 3.14.4 is affected.
- Version 3.15.0a1 and below 3.15.0a8 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.