Critical 9.2Published Sep 11, 2026

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

Updated under an hour ago (2026-10-19 09:40 UTC)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for LaciSynchroni server

Exploited in the last 30 days

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.

CVSS: 9.2 CRITICAL (v4.0, CNA)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
Weakness (CWE): CWE-287, CWE-349, CWE-602
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Sep 11, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

LaciSynchroni server lacisynchroni:server (from the name)	before 1.2.3	CNA record

References

https://github.com/LaciSynchroni/server/security/advisories/GHSA-gq4p-pxvg-6x9jx-refsource-confirm
https://github.com/LaciSynchroni/server/pull/28x-refsource-misc
https://github.com/LaciSynchroni/server/commit/5bc3efd68b738328b8faeff089dd18a826ec9ca4x-refsource-misc
https://github.com/LaciSynchroni/server/releases/tag/v1.2.3x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.