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PYSEC-2026-1239

HighCVSS 8.6 / 10
Published Jul 7, 2026·Last modified Jul 7, 2026
Affected Components(0)

No affected components available

Description

Summary

The validation for the file URI scheme falls short, and results in an attacker being able to read any file on the system. This issue only affects instances with a webdriver enabled, and ALLOW_FILE_URI false or not defined.

Details

The check used for URL protocol, is_safe_url, allows file: as a URL scheme:

https://github.com/dgtlmoon/changedetection.io/blob/e0abf0b50507a8a3d0c1d8522ab23519b3e4cdf4/changedetectionio/model/Watch.py#L11-L13

It later checks if local files are permitted, but one of the preconditions for the check is that the URL starts with file://. The issue comes with the fact that the file URI scheme is not required to have double slashes.

A valid file URI must therefore begin with either file:/path (no hostname), file:///path (empty hostname), or file://hostname/path. — Wikipedia

https://github.com/dgtlmoon/changedetection.io/blob/e0abf0b50507a8a3d0c1d8522ab23519b3e4cdf4/changedetectionio/processors/init.py#L37-L41

PoC

  1. Open up a changedetection.io instance with a webdriver configured
  2. Create a new watch: file:/etc/passwd or a similar path for your operating system. Enable webdriver mode
  3. Wait for it to be checked
  4. Open preview
  5. Notice contents of the file
Risk Scores
Base Score
8.6

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information.

Threat Intelligence
7.9

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.70%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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