CVE-2026-42857

4.6 MEDIUM 0.2% exploit odds Fix listed XSS Web app

What it 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 <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.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account, but needs a user to act. Limited direct impact.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-05-11 18:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-26 18:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 4.6 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-05-11 18:16 UTC
Last modified: 2026-10-26 18:10 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-79 · Cross-site scripting
Record status: Modified

Affected

Openedx < 2026-04-24

Attack profile CVSS 3.1 · 4.6

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-42857.md and follow it. Check whether this project is affected by CVE-2026-42857. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record