CVE-2026-79313 in Webpy
Summary
by MITRE • 09/22/2026
webpy web.py 0.76 is vulnerable to Insufficient Session Expiration. The application's session management relies on periodic cleanup to expire sessions instead of checking the last-access time when a session is loaded. As a result, an expired session whose record has not yet been cleaned up can still be replayed and used, allowing an attacker holding a previously valid session cookie to continue accessing protected resources after the configured idle timeout.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified in web.py version 0.76 represents a critical flaw in session management logic that undermines the security model of applications relying on this framework for stateful interactions. The core issue stems from an architectural decision where session expiration is handled through periodic background cleanup processes rather than real-time validation upon each request. This design choice creates a temporal window during which sessions remain active despite having exceeded their configured idle timeout limits, effectively allowing stale credentials to be reused by unauthorized actors who have obtained them through various means such as cross-site scripting attacks or network interception.
From a technical perspective, the flaw lies in the asynchronous nature of session cleanup mechanisms compared to the synchronous nature of request handling. When a user logs out or remains inactive for longer than the specified idle timeout period, the server marks the session record as expired but does not immediately invalidate it at the application layer. Instead, it relies on a separate thread or scheduled task to eventually purge these records from storage. During this interval, if an attacker possesses a valid session cookie that has technically expired according to business logic rules, they can still submit requests using that identifier. The server processes these requests because the underlying data structure containing the session state has not yet been removed or flagged as invalid by the cleanup routine, thereby bypassing intended access controls and authentication checks.
This behavior directly impacts confidentiality and integrity within web applications built on this framework. An attacker leveraging a replayed expired session can maintain persistent access to protected resources without needing to re-authenticate or obtain new credentials. This is particularly dangerous in environments where sensitive data is accessed via shared workstations, public networks, or when users fail to explicitly log out of their accounts. The persistence of active sessions beyond their intended lifespan increases the attack surface for privilege escalation and unauthorized data access, as the application fails to enforce strict session lifecycle policies required by modern security standards.
In terms of industry classification, this vulnerability aligns with CWE-613, which describes insufficient session expiration, a category of flaws where applications do not properly invalidate sessions after they are no longer needed or have timed out. Furthermore, from an offensive security perspective such as the MITRE ATT&CK framework, this flaw facilitates techniques related to Session Hijacking and Credential Replay under Tactic: Persistence or Lateral Movement depending on context. Attackers can exploit this gap to maintain footholds in compromised systems without triggering alerts associated with new login attempts, making detection more difficult for intrusion prevention systems that rely heavily on authentication event monitoring rather than session state validation timestamps.
To mitigate this risk, developers must transition from relying solely on periodic cleanup tasks to implementing immediate server-side invalidation upon timeout or logout events. This involves modifying the session middleware to check the last-accessed timestamp against the current time during every request processing cycle and rejecting any requests where the difference exceeds the defined idle limit. Additionally, integrating secure cookie attributes such as HttpOnly and Secure flags can reduce the likelihood of initial credential theft via XSS attacks, while implementing short-lived access tokens alongside longer-lasting refresh mechanisms provides a more robust defense-in-depth strategy. Regular security audits focusing on session management patterns are essential to ensure compliance with OWASP guidelines for maintaining strong authentication controls across web applications.