openedx openedx-platform 302/up to 169.254.169.254 Email Notification clean_thread_html_body cross site scripting

CVSS Meta Temp Score
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CTI Interest Score
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4.0$0-$5k0.00

Summaryinfo

A vulnerability was found in openedx openedx-platform. It has been classified as problematic. This affects the function clean_thread_html_body of the component Email Notification Handler. This manipulation causes cross site scripting. The identification of this vulnerability is CVE-2026-42857. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in openedx openedx-platform. It has been declared as problematic. Affected by this vulnerability is the function clean_thread_html_body of the component Email Notification Handler. 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. The summary by CVE is:

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 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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-42857 since 04/30/2026. The exploitation appears to be easy. The attack can be launched remotely. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Upgrading to version ulmo eliminates this vulnerability. Applying the patch cddc25cd791bb78f76833896e4778f668861df12 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.0
VulDB Meta Temp Score: 4.0

VulDB Base Score: 3.5
VulDB Temp Score: 3.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.6
CNA Vector (GitHub_M): 🔒

CVSSv2info

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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: openedx-platform ulmo
Patch: cddc25cd791bb78f76833896e4778f668861df12

Timelineinfo

04/30/2026 CVE reserved
05/11/2026 +11 days Advisory disclosed
05/11/2026 +0 days VulDB entry created
05/11/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-4xv3-5j4x-q8g4
Status: Confirmed

CNA: GitHub_M
CVE: CVE-2026-42857 (🔒)

GCVE (CVE): GCVE-0-2026-42857
GCVE (VulDB): GCVE-100-362689

Entryinfo

Created: 05/11/2026 20:23
Changes: 05/11/2026 20:23 (68)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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