Phishing-Resistant MFA Isn't the Same as Credential-Free - Here's the Gap Attackers Are Finding

Phishing-Resistant MFA Isn't the Same as Credential-Free - Here's the Gap Attackers Are Finding

Week of 17 August 2026 | Compiled by Team Paringa

Black Hat USA 2026 delivered the identity research of the summer: passkeys and FIDO2 remain cryptographically sound, but the surrounding plumbing - logging, session handling, challenge validation - is where attackers are now focused. Here's what it means for anyone still issuing a credential of any kind.

SECTION 1 - What Happened This Week

🔴 "Pass-the-Passkey" research exposes 20+ new attack techniques against Entra ID and Windows 11

At Black Hat USA on 5 August, SpecterOps principal researcher Michael Grafnetter presented "Pass-the-Passkey" - a category of more than 20 distinct attack techniques affecting Windows 11, Microsoft Entra ID, major web browsers, password managers and enterprise authentication workflows. The headline finding: the underlying cryptography behind FIDO2 passkeys is intact, but the way major platforms implement the process around it opens real gaps.

One disclosed flaw, CVE-2026-34348 (CVSS 6.5), showed the Windows Event Logging Service was writing complete copies of passkey-related key material to event logs in cleartext - readable by any authenticated, unprivileged user on the machine. Researchers also flagged inadequate enforcement of challenge uniqueness, session binding, and signature-counter verification specifically in Entra ID's implementation. A second, independent research team reached similar conclusions via a separate technique.

None of this breaks passkeys as cryptography. It breaks the assumption that "we deployed FIDO2" means the job is done. NIST now mandates phishing-resistant authenticators for AAL2, and 68% of enterprises are actively deploying passkey architectures on the strength of that mandate - but a compliance checkbox and an attacker-proof implementation are two different things, and this research is the clearest evidence yet of the gap.

Sources: The Hacker News - New Passkey Attacks Can Recover Synced Private Keys or Bypass Phishing-Resistant MFA | ComplianceHub.Wiki - Pass-the-Passkey: When 'Phishing-Resistant MFA' Stops Being a Compliance Answer

This is the tell. Every credential-issuing model - password, OTP, push, even FIDO2 - creates something that has to be generated, stored, transmitted and validated correctly at every step, and every one of those steps is a place implementation can go wrong. Twenty-plus attack techniques against the platform most enterprises trust most is not a Microsoft-specific failure, it's a structural one: if there's a credential in the flow at all, there's a surface to attack. The only way to close that surface completely is to not issue one in the first place.

🟡 AiTM phishing up 146% - Microsoft's own April campaign hit 35,000 users in three days

Microsoft's Digital Defense Report confirms adversary-in-the-middle (AiTM) attacks have surged 146% year on year, driven largely by dedicated Phishing-as-a-Service platforms that put a working AiTM proxy kit in the hands of anyone willing to rent one. The mechanics haven't changed, but the scale has: in a single campaign in April 2026, attackers compromised more than 35,000 users across 13,000 organisations in 26 countries in just three days by relaying every step of the login flow through attacker-controlled infrastructure and capturing the session token the moment it was issued - after MFA had already succeeded.

That detail matters. AiTM doesn't attack the password or the MFA code - it lets the real authentication complete, then steals the session token that authentication produces. Traditional MFA (SMS, authenticator app, push) is fully exposed to this. Even FIDO2/passkey flows, absent the implementation rigor covered above, can be undermined once a session token exists to steal. Separately, Okta customers including 1Password, BeyondTrust and Cloudflare experienced follow-on session hijacking after a 2025 Okta breach exposed over 130 customers - a reminder that the identity provider itself is part of the attack surface, not just the login page.

Sources: Roundtable AI - Defending Against Adversary-in-the-Middle (AiTM) Attacks: 2026 Security Guide | Breachsense - Okta Data Breach Case Study: Session Tokens and MFA Bypass

Every mainstream MFA model - Entra, Okta included - is built around the same pattern: verify the user, then issue a credential (a session token, a cookie) that stands in for them from that point on. AiTM doesn't need to beat your MFA; it just needs to wait for the token that MFA success produces, then steal that. An architecture where no credential is ever issued in the first place removes the thing AiTM is designed to steal. That's not a feature bullet point, it's a different threat model entirely - worth understanding before your next IAM renewal conversation.

SECTION 2 - What Identity and Security Leaders Are Dealing With

The industry spent the last three years selling "phishing-resistant MFA" as the finish line. This week's research says otherwise: phishing-resistant means resistant to credential theft at the login step, not immune to everything downstream. Session token theft, implementation flaws in event logging, and AiTM proxying all operate after authentication has already technically succeeded - which means the security conversation has to move from "did you deploy FIDO2" to "does your architecture ever create something worth stealing after login." That's a harder question, and most enterprise IAM stacks aren't built to answer it yet.

Three Things Worth Watching Next Week

1. Microsoft's response to Pass-the-Passkey disclosures - CVE-2026-34348 is patched, but the broader implementation gaps in Entra ID's challenge/session handling haven't been fully addressed; watch for Patch Tuesday follow-ups.

2. Whether NIST AAL2 guidance gets revised - researchers are already asking if "phishing-resistant" as currently defined needs a session-binding requirement added, not just a credential-type requirement.

3. PhaaS platform takedowns - law enforcement activity against AiTM-as-a-service infrastructure has been sporadic; a coordinated takedown would be the first real dent in the 146% growth curve.

Questions? hello@paringa.ai

Paringa works with identity partners built around a simple principle: you can't phish, hijack or replay a credential that was never issued. If your IAM roadmap still assumes "deploy MFA and move on," we'd rather have that conversation now than after the next AiTM campaign lands. | 17 August 2026 | © Paringa Ltd