CVE-2026-31835
MediumCVSS 5.4Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
Vaultwarden versions 1.35.4 and earlier have a vulnerability in the WebAuthn authentication flow. The validate_webauthn_login() function updates persistent credential metadata (backup_eligible and backup_state flags) based on unverified authenticatorData before signature validation. An attacker who knows the user's password but cannot produce a valid WebAuthn signature can permanently modify the backup flags for that credential. If signature verification fails, the database update is not rolled back. This can lead to persistent denial of service of WebAuthn two-factor authentication. Fixed in version 1.35.5.
Risk Assessment
Risk of permanently disabling WebAuthn two-factor authentication for affected credentials, potentially allowing attacker access without 2FA.
Recommendation
Update Vaultwarden to version 1.35.5 or later.
Original NVD description (English source)
Vaultwarden is a Bitwarden-compatible server written in Rust. In versions 1.35.4 and earlier, the WebAuthn authentication flow in `validate_webauthn_login()` updates persistent credential metadata (1backup_eligible1 and 1backup_state flags1) based on unverified `authenticatorData` before signature validation is performed. An attacker who knows a user's password but cannot produce a valid WebAuthn signature can permanently modify the stored backup flags for that user's credential. If signature verification fails, the database update is not rolled back. This can result in a persistent denial of service of WebAuthn two-factor authentication for affected credentials. This issue has been fixed in version 1.35.5.