CVE-2026-55674

CRITICALPre-NVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 72% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.3Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
9.3
EG Score
9.3(medium)
EG Risk
42(Track)
EG Risk 42/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity93% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 17, 2026

Last Modified

August 18, 2026

Advisory Details (1)

Auto-updated Aug 23, 2026
Patch available. Sources: github.
github Patch Available

Cache poisoning/XSS via color scheme cookies · Advisory · discourse/discourse · GitHub

https://github.com/discourse/discourse/security/advisories/GHSA-qx4v-rg4v-pm2g

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 26× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 03:10 UTCEG score recompute
  2. 2026-08-30 01:22 UTCEPSS rescore
  3. 2026-08-29 05:38 UTCEG score recompute
  4. 2026-08-28 21:41 UTCEPSS rescore
  5. 2026-08-27 15:44 UTCEG score recompute
  6. 2026-08-27 14:25 UTCEPSS rescore
  7. 2026-08-26 16:26 UTCEG score recompute
  8. 2026-08-26 14:46 UTCEPSS rescore
  9. 2026-08-25 17:06 UTCEG score recompute
  10. 2026-08-25 13:49 UTCEPSS rescore
  11. 2026-08-24 17:55 UTCEG score recompute
  12. 2026-08-24 10:14 UTCEG score recompute
  13. 2026-08-23 03:25 UTCEG score recompute
  14. 2026-08-23 00:19 UTCEPSS rescore
  15. 2026-08-22 00:33 UTCEG score recompute
  16. 2026-08-21 23:49 UTCEPSS rescore
  17. 2026-08-21 01:32 UTCEG score recompute
  18. 2026-08-20 22:55 UTCEPSS rescore
  19. 2026-08-19 18:25 UTCEG score recompute
  20. 2026-08-19 17:04 UTCEPSS rescore
  21. 2026-08-18 15:25 UTCEG score recompute
  22. 2026-08-18 14:51 UTCEG score recompute
  23. 2026-08-18 13:48 UTCEPSS rescore
  24. 2026-08-17 16:22 UTCEG score recompute
  25. 2026-08-17 16:10 UTCEG score recompute
Show 1 more
  1. 2026-08-17 16:09 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55674?
CVE-2026-55674 is a critical vulnerability published on August 17, 2026. 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 colorschemeid (or darkschemeid) cookie to inject arbitrary HTML into a Discourse page. Because the cookie value was rendered…
When was CVE-2026-55674 disclosed?
CVE-2026-55674 was first published in the National Vulnerability Database on August 17, 2026, with the most recent update on August 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55674 actively exploited?
CVE-2026-55674 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 71.6% of all scored CVEs.
What is the CVSS score of CVE-2026-55674?
CVE-2026-55674 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-55674?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55674, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-55674

Explore →

Is Your Infrastructure Affected by CVE-2026-55674?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs