seriousm4x UpSnap up to 5.3.5 backend/pb/handlers.go pb.HandlerInitSuperuser improper authentication

Summaryinfo

A vulnerability was found in seriousm4x UpSnap up to 5.3.5 and classified as critical. This issue affects the function pb.HandlerInitSuperuser of the file backend/pb/handlers.go. The manipulation results in improper authentication. This vulnerability is identified as CVE-2026-49819. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as critical, was found in seriousm4x UpSnap up to 5.3.5. Affected is the function pb.HandlerInitSuperuser of the file backend/pb/handlers.go. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

UpSnap is a wake on lan web app. Versions 4.4.1 through 5.3.5 are vulnerable to a missing-authentication / privilege-escalation chain in `pb.HandlerInitSuperuser` (`backend/pb/handlers.go:249`), reachable as `POST /api/upsnap/init-superuser`. The vulnerable code lacks any authentication, setup token, IP allow-list, or rate limit and is gated only by a `totalSuperusers > 0` count check — a condition that is false on every fresh install — allowing an unauthenticated network-adjacent attacker to register the initial superuser account, receive a long-lived JWT, and pivot to root remote code execution at `backend/networking/wake.go:43` (`exec.CommandContext(ctx, "/bin/sh", "-c", wake_cmd)`). Version 5.4.0 fixes the issue.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-49819 since 06/01/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

Upgrading to version 5.4.0 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• seriousm4x

Name

• UpSnap

Version

• 5.3.0
• 5.3.1
• 5.3.2
• 5.3.3
• 5.3.4
• 5.3.5

Website

• Product: https://github.com/seriousm4x/UpSnap/

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