High
Security advisory
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2016-4423
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 08:39 UTC · Revision 1
Source evidence
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.
osv:CVE-2016-4423
Complete source record
{
"id": "f6e43a5972d81f5cfdeaa410a6638bb05ee3c2d69af98f77734856d625621d7f",
"url": "https://osv.dev/vulnerability/CVE-2016-4423",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2016-4423",
"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.",
"evidence": "osv:CVE-2016-4423",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2016-4423",
"aliases": [
"CVE-2016-4423",
"GHSA-whgv-8cg3-7hcm"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
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}
}
],
"modified": "2026-10-24T10:48:17.299477373Z",
"provider": "osv",
"references": [
"https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session",
"https://github.com/symfony/symfony/pull/18733"
],
"provider_metadata": {
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"related_cves": [
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"value": "CVE-2016-4423",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 441612,
"published_at": "2016-06-01T22:59:02.457+00:00"
}