CVE-2026-45720: Github.com/siderolabs/omni Omni Has A TOCTOU Race Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5x9f-6vg5-qg4m",
  "modified" : "2026-06-05T15:25:28Z",
  "published" : "2026-06-05T15:25:28Z",
  "aliases" : [ "CVE-2026-45720" ],
  "summary" : "Omni has a TOCTOU race condition that allows multiple concurrent uses of a single-use SAML session token",
  "details" : "## Summary\n\n`SAML.getSession` (`internal/pkg/auth/interceptor/saml.go`) checks the `Used` flag on a `SAMLAssertion` resource and then marks it used in two separate state operations. Because the check and the update are not atomic, concurrent requests carrying the same `saml-session` token can both observe `Used == false`, both pass validation, and both return a successful authentication context. An attacker who obtains a valid `saml-session` token can exploit this window to authenticate as the token's owner multiple times, defeating the one-time-use guarantee.\n\n## Severity\n\n- **Attack Vector:** Local: the attacker needs to either be able to intercept the local, unencrypted traffic or needs access to user's browser.\n- **Attack Complexity:** High: the attacker must first obtain a valid `saml-session` token belonging to the victim (requires a separate interception step; the token is ephemeral and single-use by design).\n- **Privileges Required:** None: no Omni account is required to carry out the race once the session token is in hand.\n- **User Interaction:** Required: the victim must initiate a SAML authentication flow to produce the session token that the attacker intercepts.\n- **Scope:** Unchanged: the impact stays within Omni's authorization boundary.\n- **Confidentiality Impact:** High: successful exploitation authenticates the attacker as the victim's email identity, granting read access to any resource accessible to that identity.\n- **Integrity Impact:** High: the attacker can confirm one or more public keys under the victim's identity (via `ConfirmPublicKey`), establishing persistent access credentials tied to the victim's account.\n- **Availability Impact:** High: if the attacker can successfully perform the attack and if the victim is a privileged Omni user, e.g., an Omni Operator or Admin, they can take Omni down.\n\n## Impact\n\n- **Session replay**: A stolen `saml-session` token can be used more than once, defeating its single-use guarantee.\n- **Multiple public key confirmations**: An attacker who steals the session can confirm N attacker-controlled public keys under the victim's identity in a single stolen session window, creating N persistent long-lived API credentials tied to the victim's account.\n- **Authentication as victim**: Any gRPC endpoint gated by the SAML interceptor can be reached as the victim's email identity during the race window.\n- **Audit log pollution**: Each raced call generates an audit entry attributed to the victim's email, obscuring the attacker's actions.\n\n## Credit\n\nThis vulnerability was discovered and reported by [bugbunny.ai](https://bugbunny.ai).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/siderolabs/omni"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.6.6"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/siderolabs/omni"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.7.0"
      }, {
        "fixed" : "1.7.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/siderolabs/omni/security/advisories/GHSA-5x9f-6vg5-qg4m"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/siderolabs/omni"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siderolabs/omni/releases/tag/v1.6.6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siderolabs/omni/releases/tag/v1.7.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-294", "CWE-367" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-05T15:25:28Z",
    "nvd_published_at" : null
  }
}