Threat reportVulnerabilityTL-2026-1842
Pass-ta-key: Novel Attack Surface in Google Password Manager Synced Passkey Authentication
Pass-ta-key: Novel Attack Surface in Google Password Manager (TL-2026-1842), also tracked as Pass-ta-key, is a critical-severity software vulnerability scored CVSS 6.5, first published 2026-08-03 and last reviewed 2026-08-10. It has no confirmed attribution, affects Google Chrome Browser, references 1 CVE (CVE-2026-34348), maps to 21 MITRE ATT&CK techniques (T1005, T1055, T1078.004), and is covered by 9 detection rules and 18 indicators of compromise.
- CVSS
- 6.5/10Critical
- CVEs
- 1Referenced vulnerabilities
- Techniques
- 21MITRE ATT&CK
- Actors
- 0Not attributed
- Detection rules
- 9SPL · KQL · Sigma
- IOCs
- 18Indicators of compromise
Key facts for TL-2026-1842
- Threat ID
- TL-2026-1842
- Also known as
- Pass-ta-key, Silver Pass-ta-key, Golden Pass-ta-key, Pass-the-Passkey
- Severity
- CRITICAL
- CVSS
- 6.5
- Status
- ACTIVE
- Category
- VULNERABILITY
- First published
- Last reviewed
- Motivation
- FINANCIAL
- Target sectors
- technology, ecommerce, finance, government administration, health, all
- Target regions
- Global
- Detection rules
- 9
- Indicators of compromise
- 18
- Updates
- 2026-08-10 · revalidated 1× · latest source
Malware and tooling in Pass-ta-key: Novel Attack Surface in Google Password Manager
Malware and tooling: Generic info-stealer
How Pass-ta-key: Novel Attack Surface in Google Password Manager works
Unit 42 (Palo Alto Networks) disclosed the 'Pass-ta-key' attack family — three novel variants exploiting design flaws in Google Password Manager's cloud authenticator architecture for synced passkeys in Chrome on Windows with TPM. All three variants enable malware on a compromised device to silently extract and replay passkey credentials without privilege escalation, user interaction, or device unlock. The Golden variant extracts the 32-byte Security Domain Secret (SDS) master key from Chrome's process memory, enabling offline decryption of all synced passkeys past and future with no rotation mechanism available.
Unit 42 researchers identified a class of attacks against Google Password Manager's cloud-based passkey synchronization architecture in Chrome on Windows (TPM-equipped systems). The attacks exploit fundamental design gaps in how the Google Cloud Authenticator handles device identity keys, user verification (UV) key registration, and the Security Domain Secret (SDS) master key lifecycle. All three variants operate without elevated privileges — standard Windows CNG API calls from an unprivileged process suffice.
**Architecture Background:** Google Password Manager syncs passkeys across devices via a cloud authenticator running in an Oak execution environment. Chrome establishes a Noise_NK_P256_AESGCM_SHA256 encrypted WebSocket to wss://enclave.ua5v.com/enclave, authenticated via OAuth2. The local device holds two TPM-backed keys: an identity key (proving device possession) and a UV key (proving user verification via Windows Hello biometric/PIN). A 32-byte Security Domain Secret (SDS) master key encrypts all synced passkey private keys, stored on-device as a cloud-authenticator-wrapped opaque blob.
**Attack 1 — Pass-ta-key (Identity Key Exploitation):** Chrome creates the TPM identity key without a key name, causing Windows to treat it as ephemeral. Chrome then calls NcryptExportKey to export it as an NCRYPT_OPAQUE_KEY_BLOB, stored as wrapped_identity_private_key in the passkey_enclave_state file. Malware extracts this blob from disk or Chrome memory and replays standard Windows CNG API calls (NCryptOpenStorageProvider, NCryptImportKey, NCryptSignHash) to sign authentication requests to the Cloud Authenticator. The cloud authenticator returns a valid assertion — the sole difference being the User Verified (UV) flag bit is unset. Relying parties that fail to validate the UV bit (eBay was confirmed vulnerable; GitHub properly enforced it) accept the forged assertion, enabling silent account takeover. eBay fixed the UV validation gap after coordinated disclosure.
**Attack 2 — Silver Pass-ta-key (UV Key Substitution):** Malware forces device re-onboarding by deleting passkey_enclave_state or issuing a device/forget command to the cloud authenticator (no access control on this operation). During re-onboarding, Chrome on Windows defers UV key creation to avoid back-to-back PIN prompts, registering the device in a uv_key_pending state. The attacker generates their own asymmetric key pair and sends a device/add_uv_key command to the cloud authenticator with the attacker-controlled public key. Critically, the cloud authenticator does not validate attestation for newly registered UV keys — it accepts any key as legitimate. This gives the attacker a permanent, reusable authentication mechanism from their own environment, even for accounts where relying parties properly enforce user verification. Unlike the basic Pass-ta-key, this bypass works regardless of UV flag validation.
**Attack 3 — Golden Pass-ta-key (SDS Master Key Extraction):** The most severe variant. The attacker triggers device re-onboarding (same mechanism as Silver), then monitors Chrome's process memory for the SDS — a 32-byte symmetric master key that decrypts all synced passkey private keys. The SDS reaches Chrome's process memory in plaintext because Google Password Manager must obtain the master key locally on iOS and Android (where no cloud authenticator is used), and Chrome follows the same recovery model on desktop. Additionally, Unit 42 found the SDS was exposed in plaintext in Chrome's device logs accessible at chrome://device-log/FIDO. Google removed this log exposure after disclosure (Issue 464305542), but the SDS remains accessible in Chrome's process memory during device onboarding. With the SDS in hand, an attacker decrypts the encrypted_private_key fields from WebauthnCredentialSpecifics records in Chrome's sync LevelDB database, recovering all passkey private keys. These keys can authenticate from the attacker's own environment without any further access to the victim's device. Critically, Google's current implementation provides no mechanism to rotate or revoke the SDS — all existing and future passkeys for the account remain decryptable.
**Related Research — CVE-2026-34348 (Windows WebAuthN Logging):** SpecterOps independently disclosed a related vulnerability where Windows 11 (and other versions) wrote complete WebAuthn assertion payloads including challenge, authenticatorData, signature, userHandle, and credential ID to the Windows Event Log (Event ID 2106, Microsoft-Windows-WebAuthN/Operational). An attacker with local log access could replay these assertions against relying parties without replay detection (including Microsoft Entra ID/login.microsoft.com). Microsoft patched on July 14, 2026, truncating logged signatures to 6 bytes. This research, presented at Black Hat USA 2026, is part of the broader 'Pass-the-Passkey' family of attacks on passkey authentication systems.
**Current Status:** As of August 3, 2026, Google has addressed the SDS log exposure but the core design vulnerabilities remain unfixed: TPM identity keys remain exportable, UV key registration lacks attestation validation, and there is no SDS rotation mechanism. The three Pass-ta-key attacks have no CVE identifiers assigned.
MITRE ATT&CK techniques used in TL-2026-1842
Collection
T1005 Data from Local System; T1119 Automated Collection
Defense Evasion
T1055 Process Injection; T1550.001 Use Alternate Authentication Material: Application Access Token
Privilege Escalation
T1078.004 Valid Accounts: Cloud Accounts
Persistence
Execution
T1106 Native API; T1204.002 Malicious File
Credential Access
T1111 Multi-Factor Authentication Interception; T1212 Exploitation for Credential Access; T1528 Steal Application Access Token; T1552.001 Credentials In Files; T1552.004 Private Keys; T1555 Credentials from Password Stores; T1555.003 Credentials from Web Browsers; T1556.006 Modify Authentication Process: Multi-Factor Authentication
Impact
T1496 Resource Hijacking; T1531 Account Access Removal
privilege-escalation
T1548 Abuse Elevation Control Mechanism
Initial Access
T1566.001 Spearphishing Attachment
Command and Control
Affected products and versions in Pass-ta-key: Novel Attack Surface in Google Password Manager
- Google — Chrome Browser
Vulnerable versions: All versions prior to SDS log exposure fix (July/August 2026) - Google — Google Password Manager (Cloud Authenticator)
Vulnerable versions: All versions — identity key exportable, UV key attestation unvalidated, SDS not rotatable - Microsoft — Windows 11
Vulnerable versions: 23H2 (before 10.0.22631.7376); 24H2 (before 10.0.26100.8875); 25H2 (before 10.0.26200.8875); 26H1 (before 10.0.28000.2269)
Fixed in: 23H2 (10.0.22631.7376+); 24H2 (10.0.26100.8875+); 25H2 (10.0.26200.8875+); 26H1 (10.0.28000.2269+) - Microsoft — Windows 10
Vulnerable versions: 1809 (before 10.0.17763.9020); 21H2 (before 10.0.19044.7548); 22H2 (before 10.0.19045.7548)
Fixed in: 1809 (10.0.17763.9020+); 21H2 (10.0.19044.7548+); 22H2 (10.0.19045.7548+) - Microsoft — Windows Server 2019
Vulnerable versions: All (before 10.0.17763.9020)
Fixed in: 10.0.17763.9020+ - eBay — eBay.com WebAuthn Implementation
Vulnerable versions: Prior to UV flag validation fix (August 2026)
Fixed in: After Unit 42 responsible disclosure
Remediation for Pass-ta-key: Novel Attack Surface in Google Password Manager
Patches
- Apply Microsoft July 14, 2026 security update (CVE-2026-34348) — truncates WebAuthn assertion signatures in Windows Event Log to 6 bytes
- Apply Google Chrome updates with SDS logging fix (Issue 464305542) — removes SDS from chrome://device-log/FIDO output
- Monitor Chromium issue tracker for future fixes: issues 464305542, 464996836, 465359916
Immediate actions
- Monitor for unexpected Chrome process memory access by unprivileged processes (EDR behavioral detection)
- Audit Windows Event Log (Event ID 2106, Microsoft-Windows-WebAuthN/Operational) for passkey assertion leakage; apply July 2026 Windows patches truncating signature fields
- Restrict local access to Chrome user profile directories: %LocalAppData%\Google\Chrome\User Data\<Profile>\Sync Data\LevelDB and passkey_enclave_state
- Deploy EDR rules detecting anomalous Windows CNG API call sequences (NCryptOpenStorageProvider, NCryptImportKey, NCryptSignHash) from non-Chrome processes
- Enable detection for unexpected device/forget or device/add_uv_key API calls to the Cloud Authenticator enclave WebSocket
Workarounds
- Use private/incognito browsing sessions for passkey authentication (avoids Windows Event Logging of assertions per SpecterOps findings)
- Consider alternative password managers (e.g., 1Password) that bypass the Windows WebAuthn API for passkey autofill
- Delete Google Password Manager data and reinitialize to force new device enrollment (does not invalidate a previously extracted SDS)
- Change Google Password Manager PIN — effectiveness against SDS extracted prior to change is unknown per researchers' open question
Longer-term hardening
- Advocate for SDS rotation/revocation mechanism from Google — current architecture has no way to invalidate an extracted master key
- Advocate for attestation validation on UV key registration in the cloud authenticator to prevent Silver Pass-ta-key
- Advocate for TPM key creation with persistent labels (per Chromium issue 398125799) to prevent identity key export
- Relying parties should enforce userVerification=required AND validate the UV flag bit in authenticator data per W3C WebAuthn specification
- Consider hardware-bound FIDO2 security keys (YubiKey, etc.) as an alternative to cloud-synced passkeys for high-value accounts
CVEs associated with Pass-ta-key: Novel Attack Surface in Google Password Manager
Weaknesses (CWE) in Pass-ta-key: Novel Attack Surface in Google Password Manager
Timeline of Pass-ta-key: Novel Attack Surface in Google Password Manager
- SpecterOps researcher Ondrej Grafnetter discovers Windows WebAuthN Event Log (Event ID 2106) logging full passkey assertion payloads including challenge, authenticatorData, signature, userHandle, and credential ID
- SpecterOps submits initial disclosure to Microsoft Security Response Center (MSRC) regarding CVE-2026-34348 — Windows Event Logging Service Information Disclosure
- Microsoft confirms the Windows WebAuthn Event Log vulnerability classified as Information Disclosure; pays $1,000 bug bounty
- Unit 42 notifies eBay and other affected relying parties about UV flag validation failures for passkey assertions; eBay confirms and fixes validation gap
- Google removes SDS from Chrome's device-log/FIDO output following Unit 42 disclosure (Issue 464305542) — mitigates one exposure vector but SDS remains accessible in Chrome process memory during re-onboarding
- Unit 42 researchers report SDS exposure in Chrome's device logging (chrome://device-log/FIDO) and UV key registration without attestation validation to Google via Chromium issue tracker
- SpecterOps presents 'Pass-the-Passkey Family of Attacks' at Black Hat USA 2026, detailing CVE-2026-34348 and related WebAuthn assertion replay vectors
- Microsoft releases Patch Tuesday security update for CVE-2026-34348 across Windows 10, 11, and Server platforms — truncates WebAuthn assertion signatures in Event ID 2106 to 6 bytes, preventing replay attacks
- Black Hat USA 2026 opens in Las Vegas (runs through 2026-08-06).
- No fix available for core design flaws: TPM identity keys remain exportable via NCryptExportKey (Chromium issue 398125799), cloud authenticator lacks UV key attestation validation (Issue 464996836), and SDS cannot be rotated or revoked — Golden Pass-ta-key remains unmitigated
- Unit 42 publishes 'Pass the Passkey: A Novel Attack Surface in Passwordless Authentication' and companion deep-dive 'Google Cloud Authenticator: The Hidden Mechanisms of Passwordless Authentication,' publicly disclosing all three Pass-ta-key attack variants with working proof-of-concept demonstrations
- SpecterOps researcher Michael Grafnetter presents 'Pass-the-Passkey Family of Attacks' at Black Hat USA 2026 — corrected presentation date; the existing record's 2026-07-14 date predates the conference.
- Dirk-jan Mollema publishes PowerShell proof-of-concept scripts fido_assertion.ps1 and hellopoc.ps1 in the ROADtools GitHub repository.
- Dirk-jan Mollema publishes 'Borrowing Windows Hello keys for authentication and persistence,' detailing a WHFB WebAuthn assertion relay for Entra ID Primary Refresh Token theft — malware in an already-unlocked Windows session can sign assertions via NCrypt/CNG without a fresh PIN/biometric prompt, obtaining a 90-day PRT and satisfying phishing-resistant Conditional Access policies.
- The Hacker News publishes consolidated coverage of all three passkey implementation-bypass disclosures (SpecterOps CVE-2026-34348, Unit 42 Pass-ta-key, and the WHFB/Entra ID PRT relay) under the shared 'Pass-the-Passkey' family framing.
Update history for TL-2026-1842
- 2026-08-10 — New Passkey Attacks Recover Synced Private Keys or Bypass Phishing-Resistant MFA (CVE-2026-34348): What changed Severity HIGH → CRITICAL and cvss_score null → 6.5 (CVE-2026-34348), on the strength of a third, more severe disclosure added to the same 'Pass-the-Passkey' family: Dirk-jan Mollema's Windows Hello for Business WebAuthn asserti
Sources cited for Pass-ta-key: Novel Attack Surface in Google Password Manager
- Pass the Passkey: A Novel Attack Surface in Passwordless Authentication
- Google Cloud Authenticator: The Hidden Mechanisms of Passwordless Authentication
- Malware Can Steal Your Google Synced Passkey Without Asking for Your Password or Fingerprint
- Google Password Manager Attacks Could Let Malware Steal Synced Passkeys
- CVE-2026-34348 - Windows Event Logging Service Information Disclosure Vulnerability
- NVD Detail - CVE-2026-34348
- SpecterOps - Pass-the-Passkey Family of Attacks (Black Hat USA 2026)
- Chromium Issue 464305542 - SDS Exposure in chrome://device-log/FIDO
- Chromium Issue 464996836 - Cloud Authenticator UV Key Attestation
- Chromium Issue 465359916 - Signature Counter Limitations in Synced Passkey Systems
- Chromium Commit cbf35bf - GPM Enclave Controller State Changes
Detection coverage for TL-2026-1842
As of 2026-08-10, Threadlinqs Intelligence publishes 9 detection rule(s) for TL-2026-1842 across Splunk SPL, Microsoft KQL and Sigma, covering 18 indicator(s) of compromise. The whole corpus is readable without an account; a free account unlocks full detection query text in Splunk SPL, Microsoft KQL and Sigma; paid tiers add raw indicator values, correlation and the MCP server. Threadlinqs MCP server · View plans.