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Vulnerability details: VCID-nsk8-bk5e-tbfh
Vulnerability ID VCID-nsk8-bk5e-tbfh
Aliases CVE-2016-4423
GHSA-whgv-8cg3-7hcm
Summary CVE-2016-4423: Large username storage in session The attemptAuthentication function in `Component/Security/Http/Firewall/UsernamePasswordFormAuthenticationListener.php` 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.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (3)
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
CWE-399 Resource Management Errors
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
epss 0.01435 https://api.first.org/data/v1/epss?cve=CVE-2016-4423
cvssv3.1_qr HIGH https://github.com/advisories/GHSA-whgv-8cg3-7hcm
cvssv3.1 7.5 https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security/CVE-2016-4423.yaml
generic_textual HIGH https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security/CVE-2016-4423.yaml
cvssv3.1 7.5 https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2016-4423.yaml
generic_textual HIGH https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2016-4423.yaml
cvssv3.1 7.5 https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2016-4423.yaml
generic_textual HIGH https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2016-4423.yaml
cvssv3.1 7.5 https://github.com/symfony/symfony
generic_textual HIGH https://github.com/symfony/symfony
cvssv3.1 7.5 https://github.com/symfony/symfony/pull/18733
generic_textual HIGH https://github.com/symfony/symfony/pull/18733
cvssv2 5.0 https://nvd.nist.gov/vuln/detail/CVE-2016-4423
cvssv3 7.5 https://nvd.nist.gov/vuln/detail/CVE-2016-4423
cvssv3.1 7.5 https://nvd.nist.gov/vuln/detail/CVE-2016-4423
generic_textual HIGH https://nvd.nist.gov/vuln/detail/CVE-2016-4423
cvssv3.1 7.5 https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
generic_textual HIGH https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
cvssv3.1 7.5 https://symfony.com/cve-2016-4423
generic_textual HIGH https://symfony.com/cve-2016-4423
cvssv3.1 7.5 http://www.debian.org/security/2016/dsa-3588
generic_textual HIGH http://www.debian.org/security/2016/dsa-3588
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2016-4423
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1902
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4423
https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security/CVE-2016-4423.yaml
https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2016-4423.yaml
https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2016-4423.yaml
https://github.com/symfony/symfony
https://github.com/symfony/symfony/pull/18733
https://nvd.nist.gov/vuln/detail/CVE-2016-4423
https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
http://www.debian.org/security/2016/dsa-3588
cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.0:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.1:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.1:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.10:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.10:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.11:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.11:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.12:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.12:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.2:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.2:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.3:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.3:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.4:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.4:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.5:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.5:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.6:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.6:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.7:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.7:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.8:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.8:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.7.9:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.7.9:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.8.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.8.0:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.8.1:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.8.1:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.8.2:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.8.2:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.8.3:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.8.3:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.8.4:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.8.4:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:2.8.5:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:2.8.5:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:3.0.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:3.0.0:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:3.0.1:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:3.0.1:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:3.0.2:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:3.0.2:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:3.0.3:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:3.0.3:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:3.0.4:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:3.0.4:*:*:*:*:*:*:*
cpe:2.3:a:sensiolabs:symfony:3.0.5:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:sensiolabs:symfony:3.0.5:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
CVE-2016-4423 https://symfony.com/cve-2016-4423
CVE-2016-4423-LARGE-USERNAME-STORAGE-IN-SESSION http://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
GHSA-whgv-8cg3-7hcm https://github.com/advisories/GHSA-whgv-8cg3-7hcm
No exploits are available.
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security/CVE-2016-4423.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2016-4423.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2016-4423.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://github.com/symfony/symfony
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://github.com/symfony/symfony/pull/18733
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: AV:N/AC:L/Au:N/C:N/I:N/A:P Found at https://nvd.nist.gov/vuln/detail/CVE-2016-4423
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2016-4423
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2016-4423
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://symfony.com/cve-2016-4423
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at http://www.debian.org/security/2016/dsa-3588
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.80628
EPSS Score 0.01435
Published At April 1, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T12:47:03.877673+00:00 GitLab Importer Import https://gitlab.com/gitlab-org/advisories-community/-/blob/main/packagist/symfony/security/CVE-2016-4423.yml 38.0.0