CWE-384: Session Fixation

Extended Description

Such a scenario is commonly observed when: A web application authenticates a user without first invalidating the existing session, thereby continuing to use the session already associated with the user. An attacker is able to force a known session identifier on a user so that, once the user authenticates, the attacker has access to the authenticated session. The application or container uses predictable session identifiers. In the generic exploit of session fixation vulnerabilities, an attacker creates a new session on a web application and records the associated session identifier. The attacker then causes the victim to associate, and possibly authenticate, against the server using that session identifier, giving the attacker access to the user's account through the active session.

Code Examples & CVEs

Demonstrative Examples

The following example shows a snippet of code from a J2EE web application where the application authenticates users with LoginContext.login() without first calling HttpSession.invalidate().

In order to exploit the code above, an attacker could first create a session (perhaps by logging into the application) from a public terminal, record the session identifier assigned by the application, and reset the browser to the login page. Next, a victim sits down at the same public terminal, notices the browser open to the login page of the site, and enters credentials to authenticate against the application. The code responsible for authenticating the victim continues to use the pre-existing session identifier, now the attacker simply uses the session identifier recorded earlier to access the victim's active session, providing nearly unrestricted access to the victim's account for the lifetime of the session. Even given a vulnerable application, the success of the specific attack described here is dependent on several factors working in the favor of the attacker: access to an unmonitored public terminal, the ability to keep the compromised session active and a victim interested in logging into the vulnerable application on the public terminal.

BadJava

private void auth(LoginContext lc, HttpSession session) throws LoginException {...lc.login();...}

The following example shows a snippet of code from a J2EE web application where the application authenticates users with a direct post to the <code>j_security_check</code>, which typically does not invalidate the existing session before processing the login request.

BadHTML

<form method="POST" action="j_security_check"><input type="text" name="j_username"><input type="text" name="j_password"></form>

Observed CVE Examples (1)

CVE-2022-2820

Website software for game servers does not proprerly terminate user sessions, allowing for possible session fixation

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-384 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-384, Session Fixation, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Apply Firewall controls for Session Fixation

MITRE associates mitigation with Architecture and Design, and Operation; the listed strategies include Firewall; recorded impacts include Gain Privileges or Assume Identity. Use these source-defined anchors to turn CWE-384 into implementation, review, and verification checks for the affected component.

CWE-384: Session Fixation — MITRE CWE

Triage CWE-384 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-384, Session Fixation, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-384

Apply MITRE's full root-cause mapping guidance when using CWE-384, Session Fixation. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-384 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-384, Session Fixation. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-384: Session Fixation?+

CWE-384: Session Fixation is a Common Weakness Enumeration (CWE) entry maintained by MITRE. Authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions. Such a scenario is commonly observed when: A web application authenticates a user without first invalidating the existing session, thereby continuing to use the session already associated with the user. An attacker is able to force a known session identifier on a user so that, once the user authenticates, the attacker has access to the authenticated session. The application or container uses predictable session identifiers. In the generic exploit of session fixation vulnerabilities, an attacker creates a new session on a web application and records the associated session identifier. The attacker then causes the victim to associate, and possibly authenticate, against the server using that session identifier, giving the attacker access to the user's account through the active session.

What are the security consequences of Session Fixation?+

If exploited, CWE-384 (Session Fixation) it can compromise Access Control, leading to outcomes such as Gain Privileges or Assume Identity.

How do you prevent or mitigate Session Fixation?+

Recommended mitigations for CWE-384 include: Invalidate any existing session identifiers prior to authorizing a new user session. For platforms such as ASP that do not generate new values for sessionid cookies, utilize a secondary cookie. In this approach, set a secondary cookie on the user's browser to a random value and set a session variable to the same value. If the session variable and the cookie value ever don't match, invalidate the session, and force the user to log on again.

Which programming languages are affected by Session Fixation?+

CWE-384 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Session Fixation?+

MITRE documents real CVEs mapped to CWE-384, including CVE-2022-2820. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-384 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-384: Session Fixation

Extended Description

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