CVE-2026-55674: critical vulnerability in discourse
Discourse: Cache poisoning/XSS via color scheme cookies
Published · Updated
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28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.3epss 0.6%
Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, an unauthenticated attacker could send a single request with a crafted color_scheme_id (or dark_scheme_id) cookie to inject arbitrary HTML into a Discourse page. Because the cookie value was rendered into a color scheme tag without escaping, the attacker could break out of the attribute and inject a tag that bypassed Discourse's nonce-based Content Security Policy, resulting in arbitrary JavaScript execution in visitors' browsers. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Affected products
discourse · discourseRelated CVEs — discourse
In the same product, most dangerous first.
CVE-2024-53991HIGHPotential Backup file leaked via Nginx in DiscourseEPSS 29.9%CVE-2021-41163CRITICALRCE via malicious SNS subscription payloadEPSS 19.8%CVE-2023-45131HIGHUnauthenticated access to new private chat messages in DiscourseEPSS 4.0%CVE-2026-28227LOWDiscourse Vulnerable to Unauthorized Topic Creation in Staff-Only Categories via Topic Timer publish_to_categoryEPSS 3.3%CVE-2022-36066CRITICALDiscourse vulnerable to RCE via admins uploading maliciously zipped fileEPSS 2.1%CVE-2024-47773HIGHAnonymous cache poisoning via XHR requests in DiscourseEPSS 1.8%