CVE-2024-39691: Matrix appservice irc Malicious Matrix Homeserver Can Leak Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w9mh-5x8j-9754",
  "modified" : "2024-07-05T21:37:31Z",
  "published" : "2024-07-05T20:06:06Z",
  "aliases" : [ "CVE-2024-39691" ],
  "summary" : "Malicious Matrix homeserver can leak truncated message content of messages it shouldn't have access to",
  "details" : "### Impact\n\nThe fix for GHSA-wm4w-7h2q-3pf7 / [CVE-2024-32000](https://www.cve.org/CVERecord?id=CVE-2024-32000) included in matrix-appservice-irc 2.0.0 relied on the Matrix homeserver-provided timestamp to determine whether a user has access to the event they're replying to when determining whether or not to include a truncated version of the original event in the IRC message. Since this value is controlled by external entities, a malicious Matrix homeserver joined to a room in which a matrix-appservice-irc bridge instance (before version 2.0.1) is present can fabricate the timestamp with the intent of tricking the bridge into leaking room messages the homeserver should not have access to.\n\n### Patches\n\nmatrix-appservice-irc 2.0.1 [drops the reliance](https://github.com/matrix-org/matrix-appservice-irc/pull/1804) on `origin_server_ts` when determining whether or not an event should be visible to a user, instead tracking the event timestamps internally.\n\n### Workarounds\n\nIt's possible to limit the amount of information leaked by setting a reply template that doesn't contain the original message. See [these lines](https://github.com/matrix-org/matrix-appservice-irc/blob/d5d67d1d3ea3f0f6962a0af2cc57b56af3ad2129/config.sample.yaml#L601-L604) in the configuration file.\n\n### References\n\n- Patch: https://github.com/matrix-org/matrix-appservice-irc/pull/1804\n\n### For more information\n\nIf you have any questions or comments about this advisory, please email us at [security at matrix.org](mailto:security@matrix.org).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "matrix-appservice-irc"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.0.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.0.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/matrix-org/matrix-appservice-irc/security/advisories/GHSA-w9mh-5x8j-9754"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-39691"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/matrix-org/matrix-appservice-irc/pull/1804"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/matrix-org/matrix-appservice-irc/commit/1835e047f269001054be4c68867797aa12372a0f"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/matrix-org/matrix-appservice-irc"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/matrix-org/matrix-appservice-irc/blob/d5d67d1d3ea3f0f6962a0af2cc57b56af3ad2129/config.sample.yaml#L601-L604"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-280", "CWE-755" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-07-05T20:06:06Z",
    "nvd_published_at" : "2024-07-05T19:15:10Z"
  }
}