CVE-2026-42084: OpenC3 COSMOS Hijacked Session Token Can Be Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-wgx6-g857-jjf7",
  "modified" : "2026-05-29T21:45:03Z",
  "published" : "2026-04-22T22:13:10Z",
  "aliases" : [ "CVE-2026-42084" ],
  "summary" : "OpenC3 COSMOS: Hijacked session token can be used to reset password for persistence",
  "details" : "### Summary\nThe OpenC3 password change functionality allows a user to change their password without providing the old password, by accepting a valid session token instead. In assumed breach scenarios, this behaviour can be exploited by an attacker who has already obtained a valid session token, to gain persistence in hijacked account (including admin) and prevent legitimate users from accessing the account.\n\n### Details\nThe design flaw in authentication model ([authentication.rb](https://github.com/OpenC3/cosmos/blob/397abec0d57972881a2e8dc10902d0dce9c27f42/openc3/lib/openc3/utilities/authentication.rb)) allows for interchangeable use of password and session tokens for user authentication As old tokens are not revoked upon password reset, an attacker who has obtained a valid session token can continue to authenticate and change the account’s password even after the victim resets it, thereby maintaining persistent control over the compromised account.\n\n### PoC\n1. Attacker is logged in user account with hijacked valid session token, but not knowing the actual password\n2. Legitimate user, as preventive action, changes his password (_password123_) using old password (_password_), that he knows, then establishes new session\n3. Attacker issues another password change request (in web proxy like Burp) supplying his still valid token as _old_password_, changing it to attacker-password, from this point preventing any other legitimate users from accessing account\n<img width=\"912\" height=\"479\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d27b5980-0326-40f8-bb39-657d7b1c95a0\" />\n<img width=\"923\" height=\"423\" alt=\"image\" src=\"https://github.com/user-attachments/assets/060d9fe1-637e-4a2d-9142-76612984ea28\" />\n\n### Impact\nPersistence of an attacker who obtained valid session token and preventing legitimate users from account access",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "openc3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.10.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "openc3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0.pre.rc1"
      }, {
        "fixed" : "7.0.0-rc3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/OpenC3/cosmos/security/advisories/GHSA-wgx6-g857-jjf7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42084"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/OpenC3/cosmos/commit/2e623714e3426d5ae81b6f8239d4a2a6937ef776"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/OpenC3/cosmos"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/OpenC3/cosmos/releases/tag/v6.10.5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/OpenC3/cosmos/releases/tag/v7.0.0-rc3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/openc3/CVE-2026-42084.yml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-620" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-22T22:13:10Z",
    "nvd_published_at" : "2026-05-04T18:16:30Z"
  }
}