CVE-2026-72724 (GCVE-0-2026-72724)

Vulnerability from cvelistv5 – Published: 2026-08-10 15:59 – Updated: 2026-08-10 15:59
VLAI
Title
Discourse: Private Chat Threat Message Disclosure via Chat Onebox Channel/Threat ID Mismatch
Summary
Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread by route thread_id independently of the route channel_id before checking whether the user can preview the selected chat channel. An authenticated user can pair a public channel ID with a private thread ID in a /onebox.json request and obtain private thread message content. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.
Severity
4.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CWE
  • CWE-639 - Authorization Bypass Through User-Controlled Key
Assigner
References
Impacted products
Vendor Product Version
discourse discourse Affected: < 2026.1.6
Affected: >= 2026.5.0-latest, < 2026.5.2
Affected: >= 2026.6.0-latest, < 2026.6.1
Affected: >= 2026.7.0-latest, < 2026.7.0
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "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"
            },
            {
              "status": "affected",
              "version": "\u003e= 2026.7.0-latest, \u003c 2026.7.0"
            }
          ]
        }
      ],
      "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, plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread by route thread_id independently of the route channel_id before checking whether the user can preview the selected chat channel. An authenticated user can pair a public channel ID with a private thread ID in a /onebox.json request and obtain private thread message content. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 4.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-639",
              "description": "CWE-639: Authorization Bypass Through User-Controlled Key",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-10T15:59:53.965Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/discourse/discourse/security/advisories/GHSA-8g98-fvfc-9w48",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/discourse/discourse/security/advisories/GHSA-8g98-fvfc-9w48"
        },
        {
          "name": "https://github.com/discourse/discourse/pull/42091",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/pull/42091"
        },
        {
          "name": "https://github.com/discourse/discourse/pull/42092",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/pull/42092"
        },
        {
          "name": "https://github.com/discourse/discourse/pull/42093",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/pull/42093"
        },
        {
          "name": "https://github.com/discourse/discourse/pull/42094",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/pull/42094"
        },
        {
          "name": "https://github.com/discourse/discourse/commit/1276d7032af8803956c74ae87ccfd976938dcd75",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/commit/1276d7032af8803956c74ae87ccfd976938dcd75"
        },
        {
          "name": "https://github.com/discourse/discourse/commit/45ab6d54076de9ca4965888974d4416d5b48e83c",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/commit/45ab6d54076de9ca4965888974d4416d5b48e83c"
        },
        {
          "name": "https://github.com/discourse/discourse/commit/49efe1d7f098f2ce7301908815a211cc9248270f",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/commit/49efe1d7f098f2ce7301908815a211cc9248270f"
        },
        {
          "name": "https://github.com/discourse/discourse/commit/dc54846f0754799591717b6018343e49524e41ce",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/discourse/discourse/commit/dc54846f0754799591717b6018343e49524e41ce"
        }
      ],
      "source": {
        "advisory": "GHSA-8g98-fvfc-9w48",
        "discovery": "UNKNOWN"
      },
      "title": "Discourse: Private Chat Threat Message Disclosure via Chat Onebox Channel/Threat ID Mismatch"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-72724",
    "datePublished": "2026-08-10T15:59:53.965Z",
    "dateReserved": "2026-08-10T13:48:09.545Z",
    "dateUpdated": "2026-08-10T15:59:53.965Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-72724\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-08-10T16:19:49.810\",\"lastModified\":\"2026-08-10T16:19:49.810\",\"vulnStatus\":\"Received\",\"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, plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread by route thread_id independently of the route channel_id before checking whether the user can preview the selected chat channel. An authenticated user can pair a public channel ID with a private thread ID in a /onebox.json request and obtain private thread message content. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"discourse\",\"product\":\"discourse\",\"versions\":[{\"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\",\"status\":\"affected\"},{\"version\":\"\u003e= 2026.7.0-latest, \u003c 2026.7.0\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N\",\"baseScore\":4.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.8,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-639\"}]}],\"references\":[{\"url\":\"https://github.com/discourse/discourse/commit/1276d7032af8803956c74ae87ccfd976938dcd75\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/commit/45ab6d54076de9ca4965888974d4416d5b48e83c\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/commit/49efe1d7f098f2ce7301908815a211cc9248270f\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/commit/dc54846f0754799591717b6018343e49524e41ce\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/pull/42091\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/pull/42092\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/pull/42093\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/pull/42094\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/discourse/discourse/security/advisories/GHSA-8g98-fvfc-9w48\",\"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

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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.
  • 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.