FKIE_CVE-2026-55674

Vulnerability from fkie_nvd - Published: 2026-08-17 16:16 - Updated: 2026-08-17 16:16
Severity
9.3 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Summary
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.
References
security-advisories@github.comhttps://github.com/discourse/discourse/security/advisories/GHSA-qx4v-rg4v-pm2g
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "discourse",
          "vendor": "discourse",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2026.1.6"
            },
            {
              "status": "affected",
              "version": "\u003e= 2026.5.0-latest, \u003c 2026.5.2"
            },
            {
              "status": "affected",
              "version": "\u003e= 2026.6.0-latest, \u003c 2026.6.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027s nonce-based Content Security Policy, resulting in arbitrary JavaScript execution in visitors\u0027 browsers. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0."
    }
  ],
  "id": "CVE-2026-55674",
  "lastModified": "2026-08-17T16:16:58.917",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 9.3,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.8,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-17T16:16:58.917",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/discourse/discourse/security/advisories/GHSA-qx4v-rg4v-pm2g"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.