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CVE-2026-54047— Laci Synchroni Backend Vulnerable to Account Takeover / User Impersonation via Client-Side Configuration Manipulation

Quick assessment

Affected
LaciSynchroni server
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Laci Synchroni 是一个用于 Dalamud 的去中心化模组与外观同步服务器及插件。后端版本 1.2.3 之前的版本在应用程序的 OAuth2 登录流程中存在身份验证不当的漏洞。该应用依赖于客户端状态，信任用户本地 文件中 对象内的 字段。用户在登录前手动编辑该本地文件，即可提供任意的 UID。由于服务器未验证经过认证的 OAuth2 身份是否与所请求的 UID 匹配，攻击者可以完全冒充任意目标用户，并以该用户身份执行操作。此问题已在版本 1.2.3 中修复。补丁修改了 中的 方法，严格将所请求的用户

CVSS 9.2 · Critical
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I. Basic Information for CVE-2026-54047

Vulnerability Information
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Vulnerability Title
Laci Synchroni Backend Vulnerable to Account Takeover / User Impersonation via Client-Side Configuration Manipulation
Source: CVE Program / CVE List V5
Vulnerability Description
Laci Synchroni is a decentralized mod and appearance sync server and plugin for Dalamud. Versions of the backend prior to 1.2.3 have an improper authentication vulnerability in the application's OAuth2 login flow. The application relies on client-side state by trusting the `UID` field inside the `Authentications` object of a user's local `config.json` file. By manually editing this local file on their PC prior to logging in, a user can supply an arbitrary UID. Because the server fails to validate that the authenticated OAuth2 identity matches the requested UID, an attacker can fully impersonate any target user and perform actions on their behalf. This issue has been resolved in version 1.2.3. The patch modifies `AuthorizeOauthAsync` inside the `SecretKeyAuthenticatorService` to strictly bind the lookup of the requested User ID (`requestedUid`) to the record of the successfully authenticated identity (`primaryUid`). The server will no longer load or return session tokens for a requested UID unless it matches the verified, authenticated database record. No known workarounds are available.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
LaciSynchroni server < 1.2.3 -

II. Public POCs for CVE-2026-54047

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III. Intelligence Information for CVE-2026-54047

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Patches & Fixes for CVE-2026-54047 (2)

Vendor Advisories for CVE-2026-54047 (1)

Vendor Pages for CVE-2026-54047 (1)

IV. Related Vulnerabilities

Same product: server
Same weakness: CWE-287

V. Comments for CVE-2026-54047

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