HOMEVULNERABILITIESCVE-2016-4423
HIGH

CVE-2016-4423

CWE-399Published: June 1, 2016· Updated: Jun 17, 2026

7.5
CVSS v3.1

Official Description

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.

NVD Source

Technical Analysis

CVE-2016-4423 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 7.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

Debian1 product(s)
debian linux
sensiolabs1 product(s)
symfony
Source: NVD CPE · 27 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
ADVISORYhttps://symfony.com/blog/cve-2016-4423-large-username-storage-in-session

All References (6)

→
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-sessionVendor Advisory
→
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-sessionVendor Advisory

Quick Facts

CVE IDCVE-2016-4423
CVSS Score7.5 / 10
SeverityHIGH
WeaknessCWE-399
CISA KEVNo
Affected2 vendor(s)
PublishedJun 1, 2016

Related CVEs (CWE-399)

CVE-2007-5332
10.0
CVE-2011-3488
10.0
CVE-2015-8104
10.0
CVE-2008-3641
10.0
CVE-2009-2464
10.0
CVE-2009-3103
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2016-4423 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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