Vulnerability Report

CVE-2016-4423

Title: Sensiolabs Symfony Denial of Service (DoS)

DoS

Proof Of Concept

No public PoC currently indexed for CVE-2016-4423.

CWE Category CWE-399

Published Date Jun 01, 2016

Modified Date Jun 17, 2026

Exploit Status Not Found

Score 7.5 CVSS v3.0

Exploit Probability (EPSS)

1.86%

Vulnerability Summary

CVE-2016-4423: The attemptAuthentication function in Component/Security/Http/Firewall/UsernamePasswordFormAuthenticationListener.php in Symfony before 2.3.41, 2.7.x before 2.7.13, 2.8.x before 2.8.6, and 3.0.x before 3.0.6 does not limit the length of a username stored in a session, which allows remote attackers to cause a denial of service (session storage consumption) via a series of authentication attempts with long, non-existent usernames.

Impacted Vendors

sensiolabs 1

auth0 1

Reference Links

http://www.debian.org/security/2016/dsa-3588 https://github.com/symfony/symfony/pull/18733 https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session http://www.debian.org/security/2016/dsa-3588 https://github.com/symfony/symfony/pull/18733 https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session

CVSS v3.0

Source Entity [email protected]

Severity HIGH

7.5

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v2.0

Source Entity [email protected]

Severity MEDIUM

5.0

Access Vector

N/A

Authentication

N/A

RAW VECTOR AV:N/AC:L/Au:N/C:N/I:N/A:P

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2016-4423 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

June 17, 2026 MODIFIED

Vulnerability data updated via NVD.

May 06, 2026 MODIFIED

Vulnerability data updated via NVD.

April 12, 2025 MODIFIED

Vulnerability data or affected products updated.

June 01, 2016 PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector NETWORK

Complexity LOW

Privileges N/A

Interaction NONE

CVSS Vector String


                                    CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Stack

No specific products linked.