CVE-2026-54047: LaciSynchroni server · Improper Authentication
Affects LaciSynchroni serverSource CVE Database V5
Not known to be exploited · CVSS 9.2 Critical : upgrade to 1.2.3 as a priority.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.2.3
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 11 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade server and lacisynchroni/server to 1.2.3.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LaciSynchroniserver | Affected
| Fixed in
|
GitHublacisynchroni/serverpkg:github/lacisynchroni/serverOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade Laci Synchroni server to version 1.2.3 or later, where the vulnerability is fixed. The patch enforces server-side validation that the authenticated OAuth2 identity matches the requested UID, preventing impersonation. No known workarounds exist, so applying the official fix is required.
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.
References
- github.com/LaciSynchroni/server/security/advisories/GHSA-gq4p-pxvg-6x9j (opens in a new tab)
- github.com/LaciSynchroni/server/pull/28 (opens in a new tab)
- github.com/LaciSynchroni/server/commit/5bc3efd68b738328b8faeff089dd18a826ec9ca4 (opens in a new tab)
- github.com/LaciSynchroni/server/releases/tag/v1.2.3 (opens in a new tab)