CVE-2026-42857

Open edX Platform enables the authoring and delivery of online learning at any scale. The HTML sanitizer clean_thread_html_body() used for discussion notification emails fails to remove <style> tags from user-generated discussion post content. This content is rendered with Django's |safe template filter in email notification templates, allowing any enrolled student to inject arbitrary CSS into email notifications sent to other users. This enables email tracking (IP address disclosure), content spoofing, and phishing attacks. This vulnerability is fixed with commit cddc25cd791bb78f76833896e4778f668861df12.

CVSS v3 4.6 MEDIUM

4.6^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.1 / Impact : 2.5

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction REQUIRED

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/openedx/openedx-platform/commit/cddc25cd791bb78f76833896e4778f668861df12	Patch
https://github.com/openedx/openedx-platform/security/advisories/GHSA-4xv3-5j4x-q8g4	Exploit Vendor Advisory
https://github.com/openedx/openedx-platform/security/advisories/GHSA-4xv3-5j4x-q8g4	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:openedx:openedx:*:*:*:*:*:*:*:*

History

13 May 2026, 16:16

Type	Values Removed	Values Added
First Time		Openedx openedx Openedx
References	~~() https://github.com/openedx/openedx-platform/commit/cddc25cd791bb78f76833896e4778f668861df12 -~~	() https://github.com/openedx/openedx-platform/commit/cddc25cd791bb78f76833896e4778f668861df12 - Patch
References	~~() https://github.com/openedx/openedx-platform/security/advisories/GHSA-4xv3-5j4x-q8g4 -~~	() https://github.com/openedx/openedx-platform/security/advisories/GHSA-4xv3-5j4x-q8g4 - Exploit, Vendor Advisory
CPE		cpe:2.3:a:openedx:openedx::::::::

11 May 2026, 18:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-05-11 18:16

Updated : 2026-05-13 16:16

NVD link : CVE-2026-42857

Mitre link : CVE-2026-42857

CVE.ORG link : CVE-2026-42857

JSON object : View

Products Affected

openedx

openedx

CWE

CWE-79

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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