CPython <3.16 CPU DoS via Unterminated Markup in html.parser.HTMLParser
CVE-2026-15308 Published on July 9, 2026
Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations
The incremental HTML parser (html.parser.HTMLParser) allows for CPU
denial-of-service through repeated unterminated markup declarations when
processing uncontrolled data.
Vulnerability Analysis
CVE-2026-15308 is exploitable with network access, and does not require authorization privileges or user interaction. 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 Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-15308 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-15308
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Affected Versions
Python Software Foundation CPython:- Before 3.13.15 is affected.
- Version 3.14.0 and below 3.14.7 is affected.
- Version 3.15.0a1 and below 3.15.0b4 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.