# CVE-2026-39912: v2board / Xboard Authentication Token Exposure via loginWithMailLink

> Attackers can obtain authentication tokens via the loginWithMailLink endpoint to gain full account access, including admin privileges, when mail link login is enabled.

- **Severity:** Critical 9.1 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Apr 2026
- **Updated:** 14 Jul 2026
- **Also known as:** GHSA-83h9-46h8-whf4

## What is CVE-2026-39912?

CVE-2026-39912 is a critical vulnerability in cedar2025 Xboard, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

V2Board 1.6.1 through 1.7.4 and Xboard through 0.1.9 expose authentication tokens in HTTP response bodies of the loginWithMailLink endpoint when the login_with_mail_link_enable feature is active. Unauthenticated attackers can POST to the loginWithMailLink endpoint with a known email address to receive the full authentication URL in the response, then exchange the token at the token2Login endpoint to obtain a valid bearer token with complete account access including admin privileges.

Weakness: CWE-201 (Insertion of Sensitive Information Into Sent Data)

## Which versions are affected by CVE-2026-39912?


## How do I fix CVE-2026-39912?

No fix has been published for CVE-2026-39912 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39912 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39912 exists.

Public exploit code:

- Xboard / V2Board Unauth Account Takeover - Magic Link Token Leak (CVE-2026-39912) (github_poc): https://github.com/Chocapikk/CVE-2026-39912

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39912 and fix it if it is affected.

What it is: CVE-2026-39912 is a critical vulnerability in cedar2025 Xboard, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39912 exists.

Affected product: cedar2025 Xboard. 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-2026-39912/ (Markdown: https://insights.sbomify.com/CVE-2026-39912/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39912
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39912
- OSV: https://osv.dev/vulnerability/CVE-2026-39912

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39912/
Summaries are generated and may contain mistakes; the official description above is the record.