CVE-2026-31835
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.
Does this matter?
Lower severity and a low EPSS score (0.15%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 4.0
- 5.3 MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.15% probability · 5th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-345
- Affected
- dani-garcia/vaultwarden
- Source
- security-advisories@github.com
References
- https://github.com/dani-garcia/vaultwarden/releases/tag/1.35.5Product, Release Notes
- https://github.com/dani-garcia/vaultwarden/security/advisories/GHSA-x7g7-cgx5-jhx2Exploit, Vendor Advisory
- https://github.com/dani-garcia/vaultwarden/security/advisories/GHSA-x7g7-cgx5-jhx2Exploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.