CVE-2016-4423: n/a vulnerability

CVE-2016-4423: The attemptAuthentication function in Component/Security/Http/Firewall/UsernamePasswordFormAuthenticationLi...

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.

UnknownCVSS not scoredNot KEV-listedUpdatedAug 6, 2024, 00:32 UTC (UTC+00:00)

Security readout for executives and security teams

This vulnerability affects older Symfony applications with username/password login. An attacker could repeatedly submit extremely long, non-existent usernames and cause the application’s session storage to grow until availability is affected. The issue is a denial-of-service risk, not evidence of data theft or code execution in the provided sources. Exposure is most likely in internet-facing Symfony applications running the affected versions and using the username/password form authentication flow with server-side session storage. Modern Symfony versions or applications already updated past the listed fixed releases should not be affected by this specific issue. Treat as a practical availability risk for legacy Symfony systems. Prioritize remediation where affected applications are public-facing, business-critical, or use shared session storage that could affect multiple services. Mitigation focus: Upgrade Symfony to 2.3.41, 2.7.13, 2.8.6, 3.0.6, or later supported releases.; For Debian-managed systems, review and apply the relevant DSA-3588 package updates.; Confirm application dependencies are not pinned to vulnerable Symfony branches..

Prepared: Jun 13, 2026, 14:22 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record

Severity: Unknown
CVSS: Not scored
Known Exploited: No
Published: Jun 1, 2016, 22:00 UTC (UTC+00:00)

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

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0CVSS vectors

0Timeline events

0ADP providers

3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

CVE List V5 sourceCVE List V5
https://symfony.com/blog/cve-2016-4423-large-username-storage-in-sessionCVE reference · x_refsource_CONFIRM
https://github.com/symfony/symfony/pull/18733CVE reference · x_refsource_CONFIRM

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus

n/an/an/aListed

Weakness

CWE details

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