Vulnerability · Published May 5, 2026 · Assigned by GitHub_M

CVE-2026-31835Vaultwarden WebAuthn credential metadata tampered before signature verification

Medium 5.3

In plain English

A medium-severity insufficient verification of data authenticity in vaultwarden from dani-garcia. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities).

Severity (CVSS 4.0)5.3Medium

Exploit odds (30 days)0.2%top 95.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
dani-garcia	vaultwarden	< 1.35.5

Weakness: CWE-345 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

https://github.com/dani-garcia/vaultwarden/security/advisories/GHSA-x7g7-cgx5-jhx2 x_refsource_CONFIRM
https://github.com/dani-garcia/vaultwarden/releases/tag/1.35.5 x_refsource_MISC