Vulnerability · Published Apr 9, 2026 · Assigned by VulnCheck
CVE-2026-39912v2board / Xboard Authentication Token Exposure via loginWithMailLink
Critical 9.1
In plain English
A critical-severity security flaw in Xboard from cedar2025. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
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.
Affected products (as reported)
Weakness: CWE-201 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
References
- https://chocapikk.com/posts/2026/xboard-v2board-account-takeover/ technical-description, exploit
- https://github.com/v2board/v2board/pull/981 issue-tracking
- https://github.com/cedar2025/Xboard/pull/873 issue-tracking
- https://github.com/v2board/v2board/blob/0ca47622a50116d0ddd7ffb316b157afb57d25e8/app/Http/Controllers/Passport/AuthController.php#L71 related
- https://github.com/cedar2025/Xboard/blob/1fe6531924cc1ec662a88b9ef725afcf78d660bc/app/Services/Auth/MailLinkService.php#L49 related
- https://github.com/cedar2025/Xboard/blob/1fe6531924cc1ec662a88b9ef725afcf78d660bc/app/Http/Controllers/V1/Passport/AuthController.php#L51 related
- https://github.com/cedar2025/Xboard/commit/121511523f04882ec0c7447acd9b8ebcb8a47957 patch
- https://www.vulncheck.com/advisories/v2board-xboard-authentication-token-exposure-via-loginwithmaillink third-party-advisory