CVE-2026-15308
Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations
Description
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
INFO
Published Date :
July 9, 2026, 5:16 p.m.
Last Modified :
July 9, 2026, 8:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-15308
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | CRITICAL | 28c92f92-d60d-412d-b760-e73465c3df22 | ||||
| CVSS 4.0 | CRITICAL | [email protected] | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Sanitize all HTML input data.
- Update to a fixed version of the HTML parser.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-15308.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-15308 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-15308
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-15308 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-15308 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Jul. 09, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/07/09/4 -
CVE Modified by [email protected]
Jul. 09, 2026
Action Type Old Value New Value Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Removed CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X -
CVE Modified by [email protected]
Jul. 09, 2026
Action Type Old Value New Value Added Reference https://github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9 Added Reference https://github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced Added Reference https://github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606 Added Reference https://github.com/python/cpython/commit/e9f92ac0b298292e7ff998e52cb8ccacfb27a0bd Changed Affected [{'repo': 'https://github.com/python/cpython', 'vendor': 'Python Software Foundation', 'modules': ['html.parser', 'html'], 'product': 'CPython', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.16.0', 'versionType': 'python'}], 'defaultStatus': 'unaffected'}] [{'repo': 'https://github.com/python/cpython', 'vendor': 'Python Software Foundation', 'modules': ['html.parser', 'html'], 'product': 'CPython', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.15.0', 'versionType': 'python'}], 'defaultStatus': 'unaffected'}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 09, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-15308', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-09T17:31:19.781935Z'} -
New CVE Received by [email protected]
Jul. 09, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/python/cpython', 'vendor': 'Python Software Foundation', 'modules': ['html.parser', 'html'], 'product': 'CPython', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.16.0', 'versionType': 'python'}], 'defaultStatus': 'unaffected'}] Added Description The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-400 Added Reference https://github.com/python/cpython/issues/153030 Added Reference https://github.com/python/cpython/pull/153031 Added Reference https://mail.python.org/archives/list/[email protected]/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/