---
cve: "CVE-2026-39912"
severity: "CRITICAL"
cvss: 9.1
epss: "0.6%"
vendor: "v2board"
kev: false
exploited: false
published: "2026-04-09 19:16:25"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-11-10T02:58:38+01:00"
---

# CVE-2026-39912

> 9.1 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CNA-Record (Kanon, cvelistV5)

- CNA: **VulnCheck**
- State: PUBLISHED
- Stand: 2026-07-14 20:00:18
- CNA-CVSS: **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`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **poc**
  - Automatable: **yes**
  - Technical Impact: **total**

## CVSS-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Schwachstellen-Klasse

- **CWE-201** — Insertion of Sensitive Information Into Sent Data
  The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.

## Angriffsmuster (CAPEC)

- [CAPEC-12 — Choosing Message Identifier](https://capec.mitre.org/data/definitions/12.html) _(Severity: High)_
- [CAPEC-217 — Exploiting Incorrectly Configured SSL/TLS](https://capec.mitre.org/data/definitions/217.html)
- [CAPEC-612 — WiFi MAC Address Tracking](https://capec.mitre.org/data/definitions/612.html) _(Severity: Low)_
- [CAPEC-613 — WiFi SSID Tracking](https://capec.mitre.org/data/definitions/613.html) _(Severity: Low)_
- [CAPEC-618 — Cellular Broadcast Message Request](https://capec.mitre.org/data/definitions/618.html) _(Severity: Low)_
- [CAPEC-619 — Signal Strength Tracking](https://capec.mitre.org/data/definitions/619.html) _(Severity: Low)_
- [CAPEC-621 — Analysis of Packet Timing and Sizes](https://capec.mitre.org/data/definitions/621.html) _(Severity: Low)_
- [CAPEC-622 — Electromagnetic Side-Channel Attack](https://capec.mitre.org/data/definitions/622.html) _(Severity: Low)_

## Patch verfügbar (OSV)

- 121511523f04882ec0c7447acd9b8ebcb8a47957 (Commit)

## Referenzen

- <https://chocapikk.com/posts/2026/xboard-v2board-account-takeover/>
- <https://github.com/v2board/v2board/pull/981>
- <https://github.com/cedar2025/Xboard/pull/873>
- <https://github.com/v2board/v2board/blob/0ca47622a50116d0ddd7ffb316b157afb57d25e8/app/Http/Controllers/Passport/AuthController.php#L71>
- <https://github.com/cedar2025/Xboard/blob/1fe6531924cc1ec662a88b9ef725afcf78d660bc/app/Services/Auth/MailLinkService.php#L49>
- <https://github.com/cedar2025/Xboard/blob/1fe6531924cc1ec662a88b9ef725afcf78d660bc/app/Http/Controllers/V1/Passport/AuthController.php#L51>
- <https://github.com/cedar2025/Xboard/commit/121511523f04882ec0c7447acd9b8ebcb8a47957>
- <https://www.vulncheck.com/advisories/v2board-xboard-authentication-token-exposure-via-loginwithmaillink>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-39912/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_