CVE-2025-69727

Executive Summary

CVE-2025-69727 is an Incorrect Access Control vulnerability in INDEX-EDUCATION PRONOTE, a widely used school management platform in France and other French-speaking regions. The flaw resides in the index.js and composeUrlImgPhotoIndividu components, which construct direct URLs to user profile images using predictable identifiers (user IDs and names). Due to missing authorization checks and a lack of rate-limiting, an unauthenticated attacker can enumerate and retrieve profile pictures of any user by simply guessing or knowing their user ID. This leads to a privacy breach and potential user enumeration, with a CVSS score of 5.3 (Medium). No public exploit code or Nuclei template is available, but the attack vector is straightforward and requires no authentication.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It affects a proprietary web application (PRONOTE) deployed on-premises or via cloud. The risk is primarily to the confidentiality of user profile images, which may be used for social engineering or identity mapping.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – unauthenticated.
• User Interaction: None (UI:N) – no user action needed.
• Scope: Unchanged (S:U) – impact confined to the vulnerable component.
• Confidentiality Impact: Low (C:L) – only profile images are exposed.
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability allows unauthorized access to profile images, which can be used for user enumeration, social engineering, or privacy violations. The lack of rate-limiting enables bulk scraping.

Deep Dive & Mechanics

The vulnerability exists in the PRONOTE web application, specifically in the index.js JavaScript file and the composeUrlImgPhotoIndividu server-side function. These components are responsible for generating URLs to user profile images. The URL construction relies on predictable identifiers such as user IDs (numeric or sequential) and user names. For example, a typical URL might look like:

https://example.pronote.fr/photos/individu/12345.jpg

Where 12345 is the user ID. The application fails to enforce any authorization check when serving these images. An unauthenticated request to such a URL returns the image directly, without verifying if the requester has the right to view that user's profile picture. Additionally, there is no rate-limiting on the endpoint, allowing an attacker to iterate through user IDs and download all profile images.

The root cause is a missing access control check in the image serving logic. The composeUrlImgPhotoIndividu function constructs the URL but does not validate the session or permissions of the requester. The index.js client-side code may also expose the URL pattern, making it easier for attackers to understand the structure.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// index.js (client-side)
function getPhotoUrl(userId) {
    return "/photos/individu/" + userId + ".jpg";
}

// Server-side (pseudo-code)
function composeUrlImgPhotoIndividu(userId) {
    // No authentication check
    return "/photos/individu/" + userId + ".jpg";
}

// Serving the image
app.get("/photos/individu/:id.jpg", (req, res) => {
    // No authorization check
    res.sendFile(path.join(__dirname, "photos", req.params.id + ".jpg"));
});

Patched Code (Conceptual):

// Server-side (pseudo-code)
function composeUrlImgPhotoIndividu(userId, session) {
    if (!session || !session.isAuthenticated) {
        throw new Error("Unauthorized");
    }
    // Additional check: only allow if the requester has permission to view this user's photo
    if (!hasPermission(session.userId, userId)) {
        throw new Error("Forbidden");
    }
    return "/photos/individu/" + userId + ".jpg";
}

// Serving the image
app.get("/photos/individu/:id.jpg", (req, res) => {
    if (!req.session || !req.session.isAuthenticated) {
        return res.status(401).send("Unauthorized");
    }
    if (!hasPermission(req.session.userId, req.params.id)) {
        return res.status(403).send("Forbidden");
    }
    res.sendFile(path.join(__dirname, "photos", req.params.id + ".jpg"));
});

The patch adds authentication and authorization checks before serving the image, and likely implements rate-limiting to prevent enumeration.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Deploy a vulnerable instance of PRONOTE (version < 2025.2.8) in a controlled environment.
2. Create several test user accounts with known user IDs (e.g., 1001, 1002, 1003).
3. Upload profile pictures for these users.

Exploitation Steps:

1. Identify the base URL pattern. For example, from the login page or by inspecting network requests, find the photo URL pattern.
2. Craft a direct request to a known user ID:

   GET /photos/individu/1001.jpg HTTP/1.1
   Host: target.pronote.fr
   

3. If the image is returned, the vulnerability is confirmed.
4. Enumerate user IDs by iterating through a range (e.g., 1000-2000) using a script:

   for i in $(seq 1000 2000); do
       curl -s -o /dev/null -w "%{http_code}" "https://target.pronote.fr/photos/individu/$i.jpg"
       if [ $? -eq 0 ]; then
           echo "User $i exists"
       fi
   done
   

5. Download all discovered images for offline analysis.

No public exploit code is available, but the above manual method is sufficient.

Blue Team (Defensive)

Detection:

• Monitor for sequential or rapid requests to /photos/individu/*.jpg from a single IP.
• Alert on 200 responses to unauthenticated requests for these endpoints.
• Use WAF rules to block requests to /photos/individu/ without a valid session cookie.

Hunting:

• Search logs for patterns like GET /photos/individu/[0-9]+\.jpg with no prior authentication.
• Correlate with failed login attempts from the same IP.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP GET requests to /photos/individu/[0-9]+\.jpg without a session cookie.
  • Sequential requests to the above pattern from a single source IP.
  • Unusual volume of 200 responses for image files from unauthenticated users.

• File IOCs:

  • Presence of multiple downloaded .jpg files in a short time from a single IP (on the server side, in access logs).

• Behavioral IOCs:

  • User enumeration via profile image IDs.
  • Bulk scraping of profile pictures.

Detection Engineering

YARA Rule

rule CVE_2025_69727_Profile_Image_Enumeration {
    meta:
        description = "Detects attempts to enumerate PRONOTE profile images via predictable IDs"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-69727"
    strings:
        $url_pattern = /\/photos\/individu\/[0-9]+\.jpg/
        $user_agent = "curl" nocase
        $user_agent2 = "python-requests" nocase
    condition:
        $url_pattern and (#url_pattern > 5) and ($user_agent or $user_agent2)
}

Sigma Rule

title: PRONOTE Profile Image Enumeration
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects multiple requests to PRONOTE profile image URLs without authentication
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem|startswith: '/photos/individu/'
        cs-uri-stem|endswith: '.jpg'
        cs-uri-stem|re: '\/photos\/individu\/[0-9]+\.jpg'
    condition: selection | count() by src_ip > 10 within 60s
falsepositives:
    - Legitimate bulk photo downloads by authorized users (rare)
level: medium
tags:
    - attack.t1190
    - cve.2025.69727

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-69727 PRONOTE Profile Image Enumeration"; flow:to_server; content:"GET"; http_method; content:"/photos/individu/"; http_uri; pcre:"/\/photos\/individu\/[0-9]+\.jpg/"; threshold: type both, track by_src, count 10, seconds 60; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade PRONOTE to version 2025.2.8 or later, which includes the fix.
2. If immediate upgrade is not possible, implement a WAF rule to block unauthenticated requests to /photos/individu/*.jpg.
3. Enable rate-limiting on the image endpoint to prevent enumeration.

Long-term Fixes:

• Ensure all image serving endpoints require authentication and authorization.
• Use non-predictable identifiers (e.g., UUIDs) for user images.
• Implement proper access control checks on the server side.
• Conduct a security audit of other similar endpoints.

Workarounds:

• Restrict access to the /photos/individu/ path via .htaccess or Nginx config to require a valid session.
• Monitor logs for suspicious activity and block offending IPs.

Valters IT
DevSecOps & Cyber Threat Intelligence