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.
References8
- chocapikk.com/posts/2026/xboard-v2board-account-takeover/
- github.com/cedar2025/Xboard/blob/1fe6531924cc1ec662a88b9ef725af…
- github.com/cedar2025/Xboard/blob/1fe6531924cc1ec662a88b9ef725af…
- github.com/cedar2025/Xboard/commit/121511523f04882ec0c7447acd9b…
- github.com/cedar2025/Xboard/pull/873
- github.com/v2board/v2board/blob/0ca47622a50116d0ddd7ffb316b157a…
- github.com/v2board/v2board/pull/981
- www.vulncheck.com/advisories/v2board-xboard-authentication-toke…
Metrics
- CVSS 3.1
-
9.1
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - CVSS 4.0
-
9.1
CRITICAL
Score source: CNA
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 1% percentile: 50 · as of 12 November 2026
- CWE
- CWE-201
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.