Security Digest · Vulnerability record
CVE-2026-35490: changedetection.io Vulnerable to Authentication Bypass via Decorator Ordering
changedetection.io is a free open source web page change detection tool.
CVSS 9.8 Critical EPSS 0.6% · p50
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6%, percentile 50: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 50% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
changedetection.io(PyPI) <= 0.54.7, fixed in 0.54.8. Check your lockfile, including transitive dependencies.
What it is
changedetection.io is a free open source web page change detection tool. Prior to 0.54.8, the @loginoptionallyrequired 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.
From the GitHub advisory
Summary
On 13 routes across 5 blueprint files, the @loginoptionallyrequired 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.
The developer correctly uses the decorator on 30+ other routes with the proper order, making this a classic consistency gap.
Details
Correct order (used on 30+ routes):
Weakness type: CWE-863.
Product: changedetection.io (PyPI) · Assigned by: GitHub_M · Published: 2026-04-07
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | changedetection.io | <= 0.54.7 | 0.54.8 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| dgtlmoon | changedetection.io | < 0.54.8 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| GitHub | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.64% probability of exploitation activity in the next 30 days; percentile 50.
Timeline
- — GitHub-reviewed advisory GHSA-jmrh-xmgh-x9j4 published (critical)
- — CVE record published by GitHub_M
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-jmrh-xmgh-x9j4 github.com
- CVE.org record CVE-2026-35490 cve.org
- NVD entry CVE-2026-35490 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com