changedetection.io is vulnerable to unauthenticated static path traversal
Summary
The
/static// route accepts
group="..", which causes
send_from_directory("static/..", filename) to execute. This moves the base directory up to
/app/changedetectionio, enabling
unauthenticated local file read of application source files (e.g.,
flask_app.py). Severity is
low information disclosure (C:L).
Details
The vulnerable code is in
changedetectionio/flask_app.py inside
static_content():
group = re.sub(r'[^\w.-]+', '', group.lower())
filename = re.sub(r'[^\w.-]+', '', filename.lower())
...
return send_from_directory(f"static/{group}", path=filename)
The group sanitization allows dots, so group=".." passes validation.
This results in send_from_directory("static/..", filename), effectively shifting the base directory to /app/changedetectionio and allowing reads of files in that directory.
The route is unauthenticated, so any user can retrieve source files without logging in.
> Limitation: the route only matches /static// and rejects slashes inside filename, so it cannot traverse further to arbitrary system paths like /etc/passwd. It is limited to files inside the application package directory.
PoC
1) Start an instance (example: Docker on port 5050)
docker run -d --name cdio -p 127.0.0.1:5050:5000 -v cdio-data:/datastore cdio-local
2) Reproduce
(URL-encoded traversal)
curl -i http://127.0.0.1:5050/static/%2e%2e/flask_app.py
(curl path passthrough)
curl --path-as-is -i http://127.0.0.1:5050/static/../flask_app.py
3) Observe that the response body contains Python source code from flask_app.py.
Impact
- Vulnerability type: Directory Traversal / Local File Read
- Affected users: Anyone with network access (no authentication required)
- Scope: Source files under
/app/changedetectionio
- Security impact: Internal logic exposure can aid further exploitation (Confidentiality: Low)
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.the CNA's CVSS · CVSS v3.0 or v3.1
- EG Likelihood
- 1.0% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it