CVE-2026-64857 in tirreno
Summary
by MITRE • 09/09/2026
tirreno, a security framework, has a session fixation issue in versions prior to 0.10.0. During authentication, tirreno validates the user's credentials and establishes the authenticated session, but it does not call `session_regenerate_id()` afterward. As a result, the session identifier is not rotated on login, it stays the same before and after authentication. An attacker able to fix a known session identifier in a victim's browser (for example through a network man-in-the-middle position, or a separate cross-site scripting or subdomain cookie-injection issue) could then gain access to the victim's authenticated session. The issue is fixed in v0.10.0. The session identifier is now regenerated on successful authentication, and the previous session is destroyed. There is no configuration-level workaround.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified in Tirreno security framework versions prior to 0.10.0 constitutes a critical session fixation flaw rooted in improper session management practices during the authentication lifecycle. Session fixation attacks exploit weaknesses where an application fails to issue a new, random session identifier upon successful user login. In this specific case, while Tirreno correctly validates user credentials and establishes an authenticated state, it neglects to invoke the necessary function to regenerate the session identifier. This omission means that the session token present in the victim's browser before authentication remains identical after the user logs in successfully. Consequently, if an attacker can predict or control the initial unauthenticated session ID, they retain access to that same identifier once the victim has authenticated, effectively hijacking their privileged session without needing to steal credentials directly.
From a technical perspective, this flaw aligns with CWE-384, which describes Session Fixation as a vulnerability where an attacker sets or influences a user's session identifier before authentication occurs. The absence of calling `session_regenerate_id()` after successful credential validation violates fundamental security principles for state management in web applications. By maintaining the same session ID across the transition from unauthenticated to authenticated states, the application fails to break the link between any pre-existing malicious session and the newly established privileged one. This behavior allows an attacker who has injected a known session cookie into the victim's browser environment through methods such as cross-site scripting or network-level interception to simply wait for the victim to log in with valid credentials. Once authentication is complete, the attacker can use their previously fixed session ID to impersonate the user and access all resources associated with that authenticated account.
The operational impact of this vulnerability is severe, particularly in environments where sensitive data or administrative functions are protected by standard cookie-based sessions. An adversary capable of performing a man-in-the-middle attack on unencrypted connections, or exploiting other vulnerabilities like cross-site scripting to inject cookies into subdomains, can leverage this flaw to gain unauthorized access. The attacker does not need to crack passwords or bypass multi-factor authentication; they merely need the victim to authenticate using the session ID controlled by the attacker. This leads directly to CWE-613, which covers insufficient session expiration and management, resulting in a complete compromise of user confidentiality and integrity. In high-security contexts, this could allow attackers to escalate privileges, exfiltrate sensitive data, or perform actions on behalf of legitimate users with full trust from the application backend.
Mitigation strategies for this issue primarily involve upgrading to Tirreno version 0.10.0 or later, where the developers have implemented a fix that ensures the session identifier is regenerated immediately upon successful authentication and the previous session context is destroyed. This aligns with industry best practices recommended by OWASP, specifically those addressing Session Management Cheat Sheets which mandate rotating session IDs after login to prevent fixation attacks. Since there are no configuration-level workarounds available for earlier versions, organizations relying on older releases must prioritize patching as soon as possible. Additionally, implementing secure cookie attributes such as HttpOnly and Secure can provide a layer of defense against certain vectors used to inject or steal session cookies, although these measures do not fully mitigate the core logic flaw if an attacker already controls the initial ID. Adhering to ATT&CK technique T1078, which covers Valid Accounts exploitation, highlights that this vulnerability facilitates unauthorized access by leveraging legitimate credentials through compromised session states rather than credential theft alone.