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Fencer Intel
high 7.5

CVE-2016-4423 json

Symphony Denial of Service Via Overlong Usernames

published 2016-06-01 10 y ago modified 2026-06-17 4 mo ago also GHSA-whgv-8cg3-7hcm , EUVD-2022-5580

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.9%
EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist symfony/security-http 2.3.41, 2.7.13, 2.8.6, 3.0.6
  • packagist symfony/security 2.3.41, 2.7.13, 2.8.6, 3.0.6
  • packagist symfony/symfony 2.3.41, 2.7.13, 2.8.6, 3.0.6
  • symfony Debian 14, Debian 13, Debian 12 2.8.6+dfsg-1

debian advisories DEBIAN-CVE-2016-4423

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-4423 updated cvss 4.3

php-symfony: Large username storage in session

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.86% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
packagist symfony/security-http
>=2.3.0, <2.3.41
>=2.4.0, <2.7.13
>=2.8.0, <2.8.6
>=3.0.0, <3.0.6
2.3.41
2.7.13
2.8.6
3.0.6
packagist symfony/security
>=2.3.0, <2.3.41
>=2.4.0, <2.7.13
>=2.8.0, <2.8.6
>=3.0.0, <3.0.6
2.3.41
2.7.13
2.8.6
3.0.6
packagist symfony/symfony
>=2.3.0, <2.3.41
>=2.4.0, <2.7.13
>=2.8.0, <2.8.6
>=3.0.0, <3.0.6
2.3.41
2.7.13
2.8.6
3.0.6

Classification

Weakness
  • CWE-399 Resource Management Errors

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.