CVE-2026-55420 (GCVE-0-2026-55420)

Vulnerability from cvelistv5 – Published: 2026-07-09 17:54 – Updated: 2026-07-09 17:54
VLAI
Title
Discourse: Remote code execution via pdf uploads
Summary
Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, under certain non-default configurations, processing of PDF uploads could be exploited to obtain RCE on the server. This issue is patched in 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
  • CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Assigner
References
Impacted products
Vendor Product Version
discourse discourse Affected: >= 2026.5.0-latest, < 2026.5.1
Affected: >= 2026.4.0-latest, < 2026.4.2
Affected: >= 2026.1.0-latest, < 2026.1.5
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "discourse",
          "vendor": "discourse",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2026.5.0-latest, \u003c 2026.5.1"
            },
            {
              "status": "affected",
              "version": "\u003e= 2026.4.0-latest, \u003c 2026.4.2"
            },
            {
              "status": "affected",
              "version": "\u003e= 2026.1.0-latest, \u003c 2026.1.5"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, under certain non-default configurations, processing of PDF uploads could be exploited to obtain RCE on the server. This issue is patched in 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-78",
              "description": "CWE-78: Improper Neutralization of Special Elements used in an OS Command (\u0027OS Command Injection\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-09T17:54:07.940Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3"
        },
        {
          "name": "https://github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914"
        },
        {
          "name": "https://github.com/discourse/discourse/releases/tag/v2026.1.5",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/releases/tag/v2026.1.5"
        },
        {
          "name": "https://github.com/discourse/discourse/releases/tag/v2026.4.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/releases/tag/v2026.4.2"
        },
        {
          "name": "https://github.com/discourse/discourse/releases/tag/v2026.5.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/releases/tag/v2026.5.1"
        },
        {
          "name": "https://github.com/discourse/discourse/releases/tag/v2026.6.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/releases/tag/v2026.6.0"
        }
      ],
      "source": {
        "advisory": "GHSA-7wq5-jgww-5rw3",
        "discovery": "UNKNOWN"
      },
      "title": "Discourse: Remote code execution via pdf uploads"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-55420",
    "datePublished": "2026-07-09T17:54:07.940Z",
    "dateReserved": "2026-06-16T21:48:43.125Z",
    "dateUpdated": "2026-07-09T17:54:07.940Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-55420",
      "date": "2026-07-10",
      "epss": "0.0033",
      "percentile": "0.24937"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-55420\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-07-09T18:16:54.440\",\"lastModified\":\"2026-07-09T19:33:38.837\",\"vulnStatus\":\"Undergoing Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, under certain non-default configurations, processing of PDF uploads could be exploited to obtain RCE on the server. This issue is patched in 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"discourse\",\"product\":\"discourse\",\"versions\":[{\"version\":\"\u003e= 2026.5.0-latest, \u003c 2026.5.1\",\"status\":\"affected\"},{\"version\":\"\u003e= 2026.4.0-latest, \u003c 2026.4.2\",\"status\":\"affected\"},{\"version\":\"\u003e= 2026.1.0-latest, \u003c 2026.1.5\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.6,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-78\"}]}],\"references\":[{\"url\":\"https://github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/releases/tag/v2026.1.5\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/releases/tag/v2026.4.2\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/releases/tag/v2026.5.1\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/releases/tag/v2026.6.0\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}



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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

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • 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.