SSO Authentication Bypass via Invitation Token Reuse

Flowise through 3.1.4 (Enterprise/platform mode with SSO enabled) contains an authentication bypass in the SSO login path. When an SSO callback arrives with an email matching a user whose status is INVITED, verifyAndLogin (SSOBase.ts:80-94) copies the user record from the database — including the server-stored single-use invitation tempToken — into the data passed to AccountService.register(). The register handler's token lookup, email match, and expiry checks therefore pass trivially against the server's own token instead of a caller-supplied one, and the account and its organization membership are flipped to ACTIVE. As a result, anyone able to authenticate at any configured SSO provider using a pending invitee's email address as the email claim can take over that invitation and obtain the invited user's access to the organization without ever possessing the emailed invitation token, for as long as the invitation is valid (24 hours by default). At the time of the advisory no patched v

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This CVE exploits attack patterns that Casky's 283matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

Flowise versions through 3.1.4 contain a critical authentication bypass vulnerability in their SSO implementation when Enterprise mode is enabled with single sign-on. The flaw occurs in the SSOBase.ts verifyAndLogin function, which improperly handles invitation tokens during SSO callback processing. When an SSO callback arrives with an email matching an INVITED user, the system copies the database user record—including the server-stored, single-use invitation tempToken—directly into the registration request. This allows attackers to bypass authentication checks by reusing these temporary tokens, effectively gaining unauthorized access to accounts without proper credential validation. Organizations using Flowise with SSO enabled for multi-tenant or enterprise deployments are immediately at risk, as threat actors can leverage this to compromise user accounts and escalate privileges within the platform.

Casky.ai's 283 mapped security skills detect the attack patterns underlying this vulnerability by analyzing both MITRE ATT&CK Technique TA0004 (Privilege Escalation) and TA0006 (Credential Access) behaviors. Practitioners using Casky would observe findings highlighting improper token validation in authentication workflows, detection of reused or replayed authentication artifacts, and anomalous account registration patterns where invitation tokens persist beyond their intended single-use lifecycle. Claude AI's extended reasoning capabilities identify the logical flaw: the register handler's token lookup, email match, and expiry checks pass trivially because they validate against the same copied token rather than enforcing fresh validation. This manifests as suspicious SSO callback sequences where invitation states should be consumed but instead enable unauthorized access—a pattern that distinguishes this from standard authentication failures and points directly to the architectural design flaw in token handling.

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Shodan Exposure

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GreyNoise Signal

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283 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-100606.

abusing-dpapi-for-credential-access

red teaming · high

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abusing-shadow-credentials-for-privesc

red teaming · high

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Access with Stolen Session Cookie

identity access management · low

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MITRE ATT&CK Techniques

TA0004 TA0006

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