lepture mistune up to 3.2.0 Python Markdown Parser render_block_image cross site scripting

CVSS Meta Temp Score
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CTI Interest Score
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5.0$0-$5k0.00

Summaryinfo

A vulnerability was found in lepture mistune up to 3.2.0. It has been declared as problematic. The impacted element is the function render_block_image of the component Python Markdown Parser. Executing a manipulation can lead to cross site scripting. This vulnerability is tracked as CVE-2026-44899. The attack can be launched remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in lepture mistune up to 3.2.0. It has been declared as problematic. This vulnerability affects the function render_block_image of the component Python Markdown Parser. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:\.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-44899 since 05/07/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 3.2.1 eliminates this vulnerability. The upgrade is hosted for download at github.com.

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Productinfo

Vendor

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.0
VulDB Meta Temp Score: 5.0

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 6.1
NVD Vector: 🔒

CNA Base Score: 4.7
CNA Vector (GitHub_M): 🔒

CVSSv2info

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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: mistune 3.2.1

Timelineinfo

05/07/2026 CVE reserved
05/26/2026 +19 days Advisory disclosed
05/26/2026 +0 days VulDB entry created
06/01/2026 +6 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-ccfx-mfmx-2fx9
Status: Confirmed

CVE: CVE-2026-44899 (🔒)
GCVE (CVE): GCVE-0-2026-44899
GCVE (VulDB): GCVE-100-365812

Entryinfo

Created: 05/26/2026 23:33
Updated: 06/01/2026 13:44
Changes: 05/26/2026 23:33 (67), 06/01/2026 13:44 (11)
Complete: 🔍
Cache ID: 216::103

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