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Technical Analysis: How CVE-2023-0227 Works
CVE-2023-0227 is an Insufficient Session Expiration vulnerability affecting pyload, an open-source download manager written in Python. The root cause is the application’s failure to properly invalidate user sessions when permissions are changed or a user logs out.
The Flaw in Session Management
1. Session Persistence After Logout:
- When a user logs out, their session token remains valid in the backend session store (e.g., filesystem cache).
- The application does not destroy the session data or revoke the associated token.
2. Session Reuse After Permission Changes:
- If an administrator reduces a user’s permissions (e.g., removes admin rights), the session already authenticated for that user continues to function with its original privilege level.
- No mechanism exists to re‑evaluate permissions on each request or to force a session refresh after permission changes.
3. Attack Vector:
- An attacker who captures a valid session token (e.g., via XSS, network sniffing, or physical access) can reuse it indefinitely until the token’s natural expiration.
- The attacker can perform actions on behalf of the original user, even after that user’s account permissions have been reduced or the user has explicitly logged out.
4. Affected Versions:
- All pyload versions prior to 0.5.0b3.dev36 are vulnerable.
5. Impact:
- Unauthorized access to sensitive data and functions.
- Ability to bypass permission changes, leading to privilege escalation in some scenarios.
- Increased risk of session hijacking and account takeover.
The vulnerability was fixed in pyload version 0.5.0b3.dev36 by implementing proper session invalidation on logout and permission changes, and by enforcing permission checks on each authenticated request.
DailyCVE Form
Platform: Web App
Version: <0.5.0b3.dev36
Vulnerability: Session Not Invalidated
Severity: Medium (6.5)
Date: 12‑Jan‑2023
Prediction: Patch released 12‑Jan‑2023
What Undercode Say
- bash commands to test session persistence:
Capture session cookie after login curl -i -X POST http://pyload.local/login -d "username=admin&password=pass" Use captured cookie to access protected API after logout curl -i -H "Cookie: session=CAPTURED_COOKIE" http://pyload.local/api/getData
- Python snippet to demonstrate permission bypass:
import requests s = requests.Session() s.post('http://pyload.local/login', data={'username':'user','password':'pass'}) Admin reduces user's permissions in the background The session still has full access resp = s.get('http://pyload.local/api/adminOnlyFunction') print(resp.status_code) 200 even after permissions removed
Exploit
- Session fixation after logout: An attacker with a valid session token can reuse it even after the user logs out, because the backend session store retains the token until its natural expiration (e.g., 24 hours).
- Permission bypass: When an administrator reduces a user’s privileges, the user’s already‑authenticated session continues to operate with the original, higher privileges.
- Automated exploitation: Attackers can script session reuse by extracting the token once and then using it repeatedly for all API calls.
Protection from this CVE
- Upgrade to pyload 0.5.0b3.dev36 or later, where session invalidation on logout and permission changes is implemented.
- Apply the official patch that forces permission re‑evaluation on every authenticated request.
- Manual workaround (prior to patching): Configure the application to use a very short session timeout (e.g., 5 minutes) and enforce re‑authentication for sensitive operations.
- Network controls: Restrict access to the pyload web interface to trusted IP addresses only, and use a VPN for remote access.
Impact
- Confidentiality: High – session tokens can be reused to read sensitive data.
- Integrity: None – the vulnerability does not directly allow modification of data.
- Availability: None – the flaw does not affect service uptime.
- CVSS v3.1 Base Score: 6.5 (Medium), vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
- Business impact: Unauthorized access to user accounts, potential privilege escalation, and increased risk of account takeover.
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Sources:
Reported By: github.com
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