CVE-2026-55674Discourse: Cache poisoning/XSS via color scheme cookies
Updated under an hour ago ()
Does this affect you?
It affects discourse. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
Do this next
Free account, 1 product
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
- 9.3 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
- Weakness (CWE)
- CWE-79
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 18, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
discourse discourse discourse:discourse (from the name) | before 2026.1.6; from 2026.5.0-latest, < 2026.5.2; from 2026.6.0-latest, < 2026.6.1 | CNA record |
References
- https://github.com/discourse/discourse/security/advisories/GHSA-qx4v-rg4v-pm2gx-refsource-confirm
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.