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Vulnerability record · CVE-2026-49819 · published 13 August 2026

CVE-2026-49819: OS command injection vulnerability

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.

9.8 CVSS 3.1 Critical EPSS 1.1% · top 36.3% CWE-78 · OS command injectionCWE-269 · Improper privilege management Deferred
9.8CVSS 3.1 base score
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
9 Sep 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

LinkTags
https://github.com/seriousm4x/UpSnap/releases/tag/5.4.0
https://github.com/seriousm4x/UpSnap/security/advisories/GHSA-w4jr-728f-5jhq
https://github.com/seriousm4x/UpSnap/security/advisories/GHSA-w4jr-728f-5jhq

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Source: NIST National Vulnerability Database (record CVE-2026-49819), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.