---
id: CVE-2026-54047
title: >-
  Laci Synchroni is a decentralized mod and appearance sync server and plugin
  for Dalamud
summary: >-
  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 …
severity: critical
cvss: 9.2
cvssVector: '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'
cwe:
  - CWE-287
  - CWE-349
  - CWE-602
vendor: LaciSynchroni
product: server
affected:
  - server < 1.2.3
published: '2026-09-11'
updated: '2026-09-11'
sourceUpdated: '2026-09-11T20:17:14.213'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-54047'
references:
  - url: >-
      https://github.com/LaciSynchroni/server/commit/5bc3efd68b738328b8faeff089dd18a826ec9ca4
    label: security-advisories@github.com
  - url: 'https://github.com/LaciSynchroni/server/pull/28'
    label: security-advisories@github.com
  - url: 'https://github.com/LaciSynchroni/server/releases/tag/v1.2.3'
    label: security-advisories@github.com
  - url: >-
      https://github.com/LaciSynchroni/server/security/advisories/GHSA-gq4p-pxvg-6x9j
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-11T19:17:36.933448Z'
cvssSource: cna
ingestedAt: '2026-09-14T05:49:38.041Z'
epss: 0.00227
epssPercentile: 0.13642
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.