Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-49819 – Authentication Bypass leading to Root RCE – UpSnap 4.4.1–5.3.5

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-49819 is a critical authentication bypass vulnerability in UpSnap, a self-hosted Wake-on-LAN web application built with SvelteKit, Go, and PocketBase. The flaw allows an unauthenticated, network-adjacent attacker to claim the initial superuser account on a fresh installation and obtain a long-lived JWT, which can subsequently be abused to achieve arbitrary command execution as root. The issue carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: The POST /api/upsnap/init-superuser endpoint (handled by pb.HandlerInitSuperuser) is gated only by a check for whether totalSuperusers > 0. On a freshly deployed or not-yet-configured instance, this condition is always false, so the endpoint performs no authentication or authorization check at all.
  • Trigger conditions: Any attacker with network access to the instance’s setup endpoint before a legitimate administrator completes initial configuration can register themselves as the first superuser and receive a valid, long-lived JWT.
  • Attack vector: Network (AV:N), no privileges or user interaction required (PR:N/UI:N), low attack complexity (AC:L).
  • Impact: Once authenticated as superuser, the attacker can manage devices in UpSnap, including the wake_cmd field, which is passed to a shell without proper sanitization. This chains the authentication bypass into full command injection, giving the attacker root-level remote code execution on the host running UpSnap.

Affected software

  • UpSnap (seriousm4x/UpSnap) versions 4.4.1 through 5.3.5 (vulnerability introduced around December 29, 2024)
  • Fixed in version 5.4.0 and later

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade UpSnap to version 5.4.0 or later, which introduces an out-of-band setup token mechanism requiring the UPSNAP_SETUP_TOKEN environment variable and validation of the X-Setup-Token header via constant-time comparison before the initial superuser can be created.
  • If patching is not immediately possible:
    • Do not expose UpSnap’s setup/initial configuration process to untrusted networks; restrict access to the application (especially during initial deployment) to trusted, internal networks only.
    • Complete initial superuser setup immediately upon deployment, before exposing the instance to any shared or public network segment.
    • Where possible, use the upsnap superuser upsert CLI command instead of the web-based setup flow, as it enforces local-only access rather than relying on the network-reachable setup endpoint.
    • As a general practice, UpSnap should not be exposed directly to the open internet, since device wake/shutdown commands are executed via shell (potentially as root).

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge