What is CVE-2026-42857?

CVE-2026-42857 is a medium-severity vulnerability in Openedx, classified under Cross-site Scripting. CVSS score: 4.6/10. Published 2026-05-11.

How severe is CVE-2026-42857?

Medium severity. CVSS v3 base score is 4.6 out of 10.

XSS in Openedx

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 cont…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.000 (9.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.6 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N.

Affected products

Openedx
Openedx Openedx-platform — versions < cddc25cd791bb78f76833896e4778f668861df12, >= sumac, < ulmo

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)

Frequently asked questions

What is CVE-2026-42857?: CVE-2026-42857 is a medium-severity vulnerability in Openedx, classified under Cross-site Scripting. CVSS score: 4.6/10. Published 2026-05-11.
How severe is CVE-2026-42857?: Medium severity. CVSS v3 base score is 4.6 out of 10.