CVE-2026-42857: medium-severity vulnerability in openedx-platform
Open edX Platform: Stored CSS Injection in Email Notifications via Incomplete HTML Sanitization
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 4.6epss 0.2%
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:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
Affected products
openedx · openedx-platformRelated CVEs — openedx-platform
In the same product, most dangerous first.
CVE-2026-85272MEDIUMOpen edX Platform: Path traversal via prefix-bypass in safe_extractall Path ValidationEPSS 0.5%CVE-2026-55421MEDIUMOpen edX Platform: SSRF in Studio Video Download EndpointEPSS 0.5%CVE-2026-53635HIGHOpen edX Platform: Insufficient Permission on set_course_mode_price()EPSS 0.4%CVE-2026-42858HIGHOpen edX Platform: Server-Side Request Forgery (SSRF) in SAML Provider Data Sync EndpointEPSS 0.4%CVE-2026-85271MEDIUMOpen edX Platform: Stored CSS Injection in Email Digest Notifications via Unsanitized Thread Title (incomplete patch of CVE-2026-42857)EPSS 0.4%CVE-2026-53636MEDIUMOpen edX LTI OAuth Replay AttackEPSS 0.3%