CVE-2026-43891

changedetection.io has an Arbitrary Local File Read via a crafted backup restore

This is an arbitrary local file disclosure vulnerability reachable through malicious backup restore content.

Who is impacted:

• Deployments where the application process has read access to sensitive local system files.
• Docker or host-mounted environments where secrets, config files, or operational artifacts are explicitly readable by the service.

What can be exposed:

• Arbitrary System Files: Core operating system files (e.g., /etc/passwd, /proc/self/environ), system-level configurations, and host metrics.
• Application Data: Internal records and files residing under the /datastore directory.
• Secrets & Artifacts: Application-local configuration files, API tokens, database credentials, and other sensitive artifacts accessible to the application process.

By accessing the backup restore functionality and importing a crafted archive, an attacker can exploit the application's fail-open path validation. The confidentiality impact is exceptionally high because, once the payload is ingested, the application can be manipulated to disclose arbitrary local system files and highly sensitive environment variables directly through standard UI or API responses.

CVE-2026-43891 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.55.1); upgrading removes the vulnerable code path.

Kodem intelligence

The application should treat all paths restored from history.txt as untrusted input.

The root cause is in changedetectionio/model/Watch.py, where values containing path separators are currently accepted as filesystem paths and preserved if the referenced file already exists.

The fix should be:

1. Never trust absolute or external paths from history.txt.
2. Normalize every history entry to os.path.basename(v).
3. Join the normalized filename to self.data_dir.
4. Skip the entry if the resolved file does not exist inside the watch directory.

Suggested code change:

snapshot_fname = os.path.basename(v.strip())
resolved_path = os.path.join(self.data_dir, snapshot_fname)

if not os.path.exists(resolved_path):
    logger.warning(
        f"Skipping unsafe or missing history entry for {self.get('uuid')}: {v!r}"
    )
    continue

tmp_history[k] = resolved_path

This ensures restored history entries can only reference files inside the watch's own data directory and prevents arbitrary local file reads through Preview or the history API.

1. What is CVE-2026-43891? CVE-2026-43891 is a high-severity security vulnerability in changedetection.io (pip), affecting versions <= 0.54.10. It is fixed in 0.55.1.
2. How severe is CVE-2026-43891? CVE-2026-43891 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of changedetection.io are affected by CVE-2026-43891? changedetection.io (pip) versions <= 0.54.10 is affected.
4. Is there a fix for CVE-2026-43891? Yes. CVE-2026-43891 is fixed in 0.55.1. Upgrade to this version or later.
5. Is CVE-2026-43891 exploitable, and should I be worried? Whether CVE-2026-43891 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-43891 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-43891? Upgrade changedetection.io to 0.55.1 or later.