CVE-2026-42857: Open edX Platform enables the authoring and delivery of online learning at any scale

Q: How do I fix CVE-2026-42857?

openedx: upgrade to 2026-04-24. Exact commands for each OS are on this page.

Q: Is CVE-2026-42857 being exploited?

CVE-2026-42857 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-42857 affect?

CVE-2026-42857 affects openedx. Severity is medium (CVSS 4.6). 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 conte

Routine

MEDIUM 4.6UPGRADE

CVE-2026-42857 is a medium-severity flaw (CVSS 4.6) affecting openedx. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	4.6 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.2% (top 92%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-05-11
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: openedx

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-11 18:16 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

openedx openedx UPGRADE

Affected: < 2026-04-24

Fixed in: 2026-04-24

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy openedx || rpm -q openedx || openedx --version

2. UPGRADE to 2026-04-24 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade openedx

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openedx

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42857?

openedx: upgrade to 2026-04-24. Exact commands for each OS are on this page.

Is CVE-2026-42857 being exploited?

CVE-2026-42857 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42857 affect?

CVE-2026-42857 affects openedx. Severity is medium (CVSS 4.6). 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 conte

How urgent is CVE-2026-42857?

Priority 23/100. Public exploit reference

Software pages

Django vulnerabilities

Related CVEs

CVE-2026-42858 HIGH 8.5 UPGRADE Open edX Platform enables the authoring and delivery of online learning at any scale

References

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