# CVE-2016-4423: Symphony Denial of Service Via Overlong Usernames

Source: https://junglewise.ai/threats/cve-2016-4423-symphony-denial-of-service-via-overlong-usernames  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2022-05-17  
License: CC BY 4.0 with a link back

CVE-2016-4423 · Severity: low · CVSS 3 · Published 2022-05-17

Symphony Denial of Service Via Overlong Usernames

Technologies: [symfony/security (Packagist)](https://junglewise.ai/threats/technologies/symfony-security), [symfony/security-http (Packagist)](https://junglewise.ai/threats/technologies/symfony-security-http), [symfony/symfony (Packagist)](https://junglewise.ai/threats/technologies/symfony-symfony). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is CVE-2016-4423 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-4423 being exploited in the wild.

**How severe is CVE-2016-4423?** Low severity, with a CVSS score of 3, published 17 May 2022.

**Which products and versions are affected?** symfony/security (Packagist) ECOSYSTEM:introduced=2.3.0,fixed=2.3.41; symfony/security-http (Packagist) ECOSYSTEM:introduced=2.3.0,fixed=2.3.41; symfony/symfony (Packagist) ECOSYSTEM:introduced=2.3.0,fixed=2.3.41.

**Is there a fix for CVE-2016-4423?** Yes. symfony/security (Packagist): upgrade to 2.3.41 or later; symfony/security-http (Packagist): upgrade to 2.3.41 or later; symfony/symfony (Packagist): upgrade to 2.3.41 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2016-4423?** Check whether you run symfony/security (Packagist), symfony/security-http (Packagist) or symfony/symfony (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- symfony/security (Packagist): upgrade to 2.3.41 or later

  ```sh
  composer require symfony/security:^2.3.41
  ```

- symfony/security-http (Packagist): upgrade to 2.3.41 or later

  ```sh
  composer require symfony/security-http:^2.3.41
  ```

- symfony/symfony (Packagist): upgrade to 2.3.41 or later

  ```sh
  composer require symfony/symfony:^2.3.41
  ```


## Affected products

- symfony/security (Packagist) ECOSYSTEM:introduced=2.3.0,fixed=2.3.41
- symfony/security-http (Packagist) ECOSYSTEM:introduced=2.3.0,fixed=2.3.41
- symfony/symfony (Packagist) ECOSYSTEM:introduced=2.3.0,fixed=2.3.41

## Identifiers

- CVE-2016-4423
- GHSA-whgv-8cg3-7hcm

## Related threats

- [Symfony YAML stack exhaustion in inline lexer](https://junglewise.ai/threats/cve-2026-109413-in-symfony-yaml-prior-to-versions-5-4-54-6-4-45-7-4-18-and-8-1-6)
- [Symfony HTTP Foundation ReDoS in HeaderUtils::split()](https://junglewise.ai/threats/cve-2026-108082-symfony-is-a-php-framework-for-web-and-console-applications-and)
- [Symfony Routing improper dot-segment encoding in UrlGenerator](https://junglewise.ai/threats/cve-2026-48784-symfony-routing-improper-dot-segment-encoding-in-urlgenerator)
- [Symfony HtmlSanitizer XSS via incomplete URL attribute sanitization](https://junglewise.ai/threats/cve-2026-48761-symfony-htmlsanitizer-xss-via-incomplete-url-attribute)
- [Symfony HtmlSanitizer visual spoofing via percent-encoded BiDi characters](https://junglewise.ai/threats/cve-2026-48760-symfony-htmlsanitizer-visual-spoofing-via-percent-encoded-bidi)