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

> Attackers can permanently disable WebAuthn two-factor authentication for users by tampering with credential metadata before signature verification occurs.

- **Severity:** Medium 5.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 May 2026
- **Updated:** 6 May 2026
- **Also known as:** GHSA-x7g7-cgx5-jhx2

## What is CVE-2026-31835?

CVE-2026-31835 is a medium-severity vulnerability in dani-garcia vaultwarden, published on 5 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### 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.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-31835?

It affects 1 product.


Products: Dani-Garcia Vaultwarden.

## How do I fix CVE-2026-31835?

No fix has been published for CVE-2026-31835 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-31835 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31835 exists.

## Other vulnerabilities in dani-garcia vaultwarden

- [CVE-2024-55225](https://insights.sbomify.com/CVE-2024-55225/): Vaultwarden vulnerable to user impersonation (critical 9.8)
- [CVE-2024-55224](https://insights.sbomify.com/CVE-2024-55224/): Vaultwarden HTML injection vulnerability (critical 9.6)
- [CVE-2024-39924](https://insights.sbomify.com/CVE-2024-39924/): Privilege escalation in n/a (high 8.8)
- [CVE-2026-43912](https://insights.sbomify.com/CVE-2026-43912/): Vaultwarden: Cross-Org Group Binding Enables Unauthorized Read And Write Access Into Another Organization (high 8.7)
- [CVE-2026-27802](https://insights.sbomify.com/CVE-2026-27802/): Vaultwarden: Privilege Escalation via Bulk Permission Update to Unauthorized Collections by Manager (high 8.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31835 and fix it if it is affected.

What it is: CVE-2026-31835 is a medium-severity vulnerability in dani-garcia vaultwarden, published on 5 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31835 exists.

Affected product: dani-garcia vaultwarden. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31835/ (Markdown: https://insights.sbomify.com/CVE-2026-31835/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31835
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31835
- OSV: https://osv.dev/vulnerability/CVE-2026-31835

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-31835/
Summaries are generated and may contain mistakes; the official description above is the record.