7

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-45720

CVE-2026-45720: Omni has a TOCTOU race condition that allows multiple concurrent uses of a single-use SAML session token

Summary

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.

Severity

Attack Vector: Local: the attacker needs to either be able to intercept the local, unencrypted traffic or needs access to user's browser.
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).
Privileges Required: None: no Omni account is required to carry out the race once the session token is in hand.
User Interaction: Required: the victim must initiate a SAML authentication flow to produce the session token that the attacker intercepts.
Scope: Unchanged: the impact stays within Omni's authorization boundary.
Confidentiality Impact: High: successful exploitation authenticates the attacker as the victim's email identity, granting read access to any resource accessible to that identity.
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.
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.

Impact

Session replay: A stolen saml-session token can be used more than once, defeating its single-use guarantee.
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.
Authentication as victim: Any gRPC endpoint gated by the SAML interceptor can be reached as the victim's email identity during the race window.
Audit log pollution: Each raced call generates an audit entry attributed to the victim's email, obscuring the attacker's actions.

Credit

This vulnerability was discovered and reported by bugbunny.ai.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-45720

CVE-2026-45720:

7

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/siderolabs/omni	go	< 1.6.6	1.6.6
github.com/siderolabs/omni	go	>= 1.7.0, < 1.7.3	1.7.3

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a classic Time-of-check Time-of-use (TOCTOU) race condition within the SAML.getSession function located in internal/pkg/auth/interceptor/saml.go. The function's logic for validating a SAML session token involved two distinct steps: first, checking if the token had been used, and second, marking it as used. Because these two steps were not performed as a single, atomic operation, a window of opportunity existed for an attacker. By sending multiple concurrent requests with the same stolen SAML token, an attacker could have all requests pass the initial 'used' check before any of them had the chance to update the token's state to 'used'. The provided patch rectifies this by moving the check for the Used flag inside the atomic safe.StateUpdateWithConflicts operation, ensuring that checking and marking the token as used happens indivisibly. This prevents the race condition and enforces the single-use nature of the SAML session tokens.

Vulnerable functions

SAML.getSession

internal/pkg/auth/interceptor/saml.go

The function `getSession` in the `SAML` struct is vulnerable to a Time-of-check Time-of-use (TOCTOU) race condition. It checks if a SAML session token has been used and then marks it as used in two separate, non-atomic operations. This allows an attacker who intercepts a valid `saml-session` token to reuse it multiple times in concurrent requests before the system can mark it as used. Successful exploitation allows an attacker to authenticate as the victim, potentially gaining full access to the victim's resources.

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WAF Rule

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Reasoning

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