External risk intelligence

changedetection.io Authentication Bypass Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-35490

Changedetection.io is a web-based application designed to monitor and access external websites. Such tools are commonly deployed as network-accessible services to enable monitoring, often reachable via web interfaces or APIs, making them frequently internet-facing or accessible within a network perimeter.

Webtechnologies Changedetection

before 0.54.8

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A security issue was identified in the change detection tool, which could allow unauthorized access to its features. The primary concern is to determine if this tool is in use and if it is exposed in a way that could be exploited.

  • Authentication bypassed on protected routes.
  • Important for organizations using the tool.
  • Confirm relevance and assess potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending unauthenticated requests to specific routes within the changedetection.io application. This occurs because the order of decorators on certain routes was incorrectly configured, effectively bypassing the authentication checks that should have been in place. Successful exploitation allows an attacker to gain unauthorized access and potentially perform actions with administrative privileges.

  • Network access required.
  • Routes improperly registered.
  • Unauthorized access and control.

Live Threat

Current exploitation, exposure, and threat context

When authentication is bypassed, sensitive routes within changedetection.io could become accessible without proper authorization. This could allow unauthorized users to potentially view, modify, or delete monitored website data, or alter the application's configuration when supported by the advisory.

  • Monitored website data or application configuration.
  • Accessing routes without authentication checks.
  • Unauthorized data access or modification.

Operational Fix

Recommended remediation, mitigation, and detection steps

The owner of the changedetection.io application, likely an application or platform team, must first identify all instances of this tool across their environment. Confirming which instances are exposed externally or are business-critical will inform prioritization for remediation. Planning for updates during scheduled maintenance windows or coordinating with the vendor for patches is the subsequent practical move.

  • Confirm affected instances and their exposure.
  • Identify business-critical deployments.
  • Plan remediation based on risk.

Supplementary metadata

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

Frequently asked questions

What is changedetection.io used for?

changedetection.io is an open-source web application designed to monitor websites for changes. Users typically deploy it to track updates on various pages, receiving notifications when content is modified. It acts as a localized service that fetches and stores external website data for its users.

What does CWE-863 mean for CVE-2026-35490?

CWE-863 refers to 'Incorrect Authorization.' In the context of CVE-2026-35490, this weakness means the application fails to correctly enforce access controls. Because of an error in how the software processes security decorators, the intended login requirements are completely bypassed, allowing anyone to access restricted routes as if they were authorized users.

How does an attacker trigger this authentication bypass?

An attacker triggers this vulnerability by sending standard network requests to protected routes in the application. The bug is caused by a misconfiguration in the code structure; simply requesting these specific pages allows the attacker to reach them without any credentials. This does not happen if the application is running version 0.54.8 or newer, as the code order has been corrected.

Is my changedetection.io instance at risk?

If you are using a version prior to 0.54.8, your instance is vulnerable. Halo Surface Signal notes that this tool is often deployed as a network-accessible service, meaning it is frequently internet-facing or reachable within internal networks. If your instance is accessible over the network, it is susceptible to unauthorized access regardless of your specific use case.

How do I fix this security issue?

The primary step is to update your changedetection.io installation to version 0.54.8 or later. To begin, audit your environment to locate all instances of the software, particularly those that are network-accessible or handle sensitive monitoring data. Once identified, schedule the update to apply the corrected authentication logic.

References