CVE-2026-31835Public exploitNetwork attack vector

Persistent WebAuthn denial via pre-verification metadata update

Published May 5, 2026 · Updated May 5, 2026

WebAuthn authentication flaw in Vaultwarden 1.35.4 and earlier allows remote authenticated users to disable a credential's 2FA. In validate_webauthn_login(), check_and_update_backup_eligible() persists BE and BS flags parsed from unverified authenticatorData before finish_passkey_authentication() validates the signature, and a failed validation does not roll back the write. Knowledge of the user's password and a registered WebAuthn credential is required; a forged assertion can persistently prevent that credential from completing WebAuthn two-factor authentication.

CVSS severity5.3
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

WebAuthn authentication flaw in Vaultwarden 1.35.4 and earlier allows remote authenticated users to disable a credential's 2FA. In validate_webauthn_login(), check_and_update_backup_eligible() persists BE and BS flags parsed from unverified authenticatorData before finish_passkey_authentication() validates the signature, and a failed validation does not roll back the write. Knowledge of the user's password and a registered WebAuthn credential is required; a forged assertion can persistently prevent that credential from completing WebAuthn two-factor authentication.

The record

CVE
CVE-2026-31835
Published
May 5, 2026
Updated
May 5, 2026
Vendor
Dani Garcia
Product
Vaultwarden
Classifications
CWE-345, T1531
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 5, 2026CVE publishedPublication date reported by the CVE source.
  2. May 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.35.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Dani Garcia · Vaultwardenversion=< 1.35.5

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
5.3GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
T1531Account Access Removal

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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