25 Vulnerabilities in Cloud Password Managers Allow Unauthorized Access and Modifications
Researchers from ETH Zurich have uncovered 25 serious vulnerabilities in three leading cloud-based password managers : Bitwarden, LastPass, and Dashlane.
These flaws enable a malicious server to bypass zero-knowledge encryption claims, allowing unauthorized access, modification, and recovery of users’ stored passwords and vault data.
Bitwarden, LastPass, and Dashlane collectively serve over 60 million users and hold significant market share. The analysis targets their client-server interactions under a fully malicious server threat model, where servers deviate arbitrarily from protocols.
Vendors advertise “zero-knowledge encryption,” implying servers cannot access plaintext vaults even if compromised, but the researchers demonstrate repeated failures in confidentiality and integrity protections.
The 25 attacks span four categories: key escrow mechanisms, item-level vault encryption flaws, sharing features, and backwards compatibility issues.
Key Escrow Attacks
These target account recovery and SSO login mechanisms enable full vault compromise via unauthenticated keys. Bitwarden’s BW01-BW03 allow malicious auto-enrollment, key rotation, and KC conversion through key substitution upon joining organizations or dialogs. LastPass’s LP01 exploits password reset flaws similarly.
Item-Level Encryption Flaws
Flawed per-item encryption leads to integrity violations, metadata leaks, field swapping, and KDF downgrades. Bitwarden’s BW04-BW07 expose unprotected metadata, swap fields, decrypt icons, and remove iterations for brute-force. LastPass LP02-LP06 and Dashlane DL01 enable malleable vaults and replay attacks due to AES-CBC and missing bindings.
Sharing Feature Exploits
Unauthenticated public keys compromise organizations and shared vaults. Bitwarden’s BW08-BW09 inject or overwrite organizations; LastPass LP07 and Dashlane DL02 overwrite sharing keys upon joining. Impacts scale to team-wide access.
Backwards Compatibility Issues
Legacy code support triggers downgrades to insecure modes like CBC. Bitwarden’s BW10-BW12 disable protections and overwrite keys; Dashlane’s DL03-DL06 enable injections, KDF removal, and “Lucky 64” after syncs. Dashlane patched via extension 6.2544.1.
In Bitwarden, 12 attacks include malicious auto-enrollment (BW01), where unauthenticated organization public keys allow key substitution and full vault compromise upon joining any group.
LastPass faces seven issues, such as lacking ciphertext integrity with AES-CBC (LP05), enabling malleable vaults, and field swapping. Dashlane has six vulnerabilities, like transaction replay (DL01) due to shared keys across transactions, violating vault integrity.
Attack Ref Product Cause Impact Client Interaction BW01 Bitwarden Lack of Key Auth, Key Substitution Full vault compromise 1 join BW02 Bitwarden Key Substitution Full vault compromise 1 rotation BW03 Bitwarden Lack of Key Auth, Key Substitution Full vault compromise 1 dialog LP01 LastPass Lack of Key Auth Full vault compromise 1 login BW04 Bitwarden Lack of Auth Enc Read/modify metadata – BW05 Bitwarden Lack of Key Sep Field/item swapping – BW06 Bitwarden Lack of Key Sep Loss of confidentiality 1 open BW07 Bitwarden Lack of Auth Enc No brute-force protection 1 login LP02 LastPass Lack of Auth Enc Field/item swapping – LP03 LastPass Lack of Key Sep Loss of confidentiality 1 open LP04 LastPass Lack of Auth Enc No brute-force protection 1 login LP05 LastPass Lack of Auth Enc Loss of vault integrity – DL01 Dashlane Lack of Key Sep Loss of vault integrity – BW08 Bitwarden Lack of Key Auth Add users to orgs 1 sync BW09 Bitwarden Lack of Key Auth, Key Substitution Org compromise 1 join LP07 LastPass Lack of Key Auth Shared vault compromise 1 join DL02 Dashlane Lack of Key Auth Shared vault compromise 1 join BW10 Bitwarden Lack of Auth Enc Downgrade key hierarchy – BW11 Bitwarden CBC Support Loss of confidentiality 2 logins BW12 Bitwarden CBC Support Full vault compromise 2 logins DL03 Dashlane CBC Support Loss of vault integrity 104 syncs DL04 Dashlane CBC Support No brute-force protection 104 syncs DL05 Dashlane CBC Support Loss of confidentiality 105 syncs DL06 Dashlane CBC Support No brute-force protection 104 syncs LP06 LastPass Lack of Auth Enc Read/modify metadata –
Many attacks require minimal interaction, like a single login or sync, exploiting unauthenticated public keys, missing key separation, and legacy AES-CBC support. For instance, icon URL decryption leaks (BW06, LP03) reveal passwords via client requests. KDF iteration downgrades (BW07, LP04) accelerate brute-force by up to 300,000x.
Attack Hierarchies
Researchers disclosed findings responsibly : Bitwarden on January 27, 2025; LastPass on June 4, 2025; Dashlane on August 29, 2025, with 90-day remediation windows.
Bitwarden advanced fixes for several, including minimum KDF iterations and CBC removal; LastPass addressed LP03; Dashlane mitigated some CBC issues. Recommended mitigations include authenticated encryption (AE), full key separation (KS), public key authentication (PKA), and ciphertext signing (SC).
Users should update clients, enable per-item keys where available, and monitor vendor patches. The study urges formal security models for password managers akin to E2EE cloud storage. Self-hosted deployments remain vulnerable if servers are compromised.
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The post 25 Vulnerabilities in Cloud Password Managers Allow Unauthorized Access and Modifications appeared first on Cyber Security News .
25 Vulnerabilities in Cloud Password Managers Allow Unauthorized Access and Modifications
17.02.2026 05:23
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