# CVE-2019-18886: User enumeration leak using switch user functionality in Symfony

> Attackers can enumerate valid users by observing differences in response handling during unauthorized user switching attempts in the Symfony security component.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Nov 2019
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-18886, GHSA-4vpc-5jx4-cfqg

## What is CVE-2019-18886?

CVE-2019-18886 is a medium-severity vulnerability in Sensiolabs Symfony, published on 21 Nov 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Symfony 4.2.0 to 4.2.11 and 4.3.0 to 4.3.7. The ability to enumerate users was possible due to different handling depending on whether the user existed when making unauthorized attempts to use the switch users functionality. This is related to symfony/security.

Weakness: CWE-203 (Observable Discrepancy)

## Which versions are affected by CVE-2019-18886?

8 open source packages ship an affected version, including symfony/security-http and symfony/symfony. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `symfony/security-http` | Packagist | From 4.1.0 | 4.2.12 |
| `symfony/security-http` | Packagist | From 4.1.0 | 4.2.12 |
| `symfony/security-http` | Packagist | From 4.3.0 | 4.3.8 |
| `symfony/security-http` | Packagist | From 4.3.0 | 4.3.8 |
| `symfony/symfony` | Packagist | From 4.1.0 | 4.2.12 |
| `symfony/symfony` | Packagist | From 4.1.0 | 4.2.12 |
| `symfony/symfony` | Packagist | From 4.3.0 | 4.3.8 |
| `symfony/symfony` | Packagist | From 4.3.0 | 4.3.8 |

Products: Sensiolabs Symfony.

## How do I fix CVE-2019-18886?

Upgrade symfony/security-http to a fixed version for your release line: 4.2.12 or 4.3.8.

## Is CVE-2019-18886 being exploited?

There is no known exploitation of CVE-2019-18886 in the wild and no public exploit code.

## Other vulnerabilities in Sensiolabs Symfony

- [CVE-2019-11325](https://insights.sbomify.com/CVE-2019-11325/): Improper Input Validation in Symfony (critical 9.8)
- [CVE-2017-11365](https://insights.sbomify.com/CVE-2017-11365/): Symfony Incorrect Access Control (critical 9.8)
- [CVE-2019-10913](https://insights.sbomify.com/CVE-2019-10913/): Invalid HTTP method overrides allow possible XSS or other attacks in Symfony (critical 9.8)
- [CVE-2018-11407](https://insights.sbomify.com/CVE-2018-11407/): Symfony Authentication Bypass (critical 9.8)
- [CVE-2016-2403](https://insights.sbomify.com/CVE-2016-2403/): Symfony Authentication Bypass (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-18886 and fix it if it is affected.

What it is: CVE-2019-18886 is a medium-severity vulnerability in Sensiolabs Symfony, published on 21 Nov 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2019-18886 in the wild and no public exploit code.

Affected packages and fixed versions:
- symfony/security-http (Packagist): affected from 4.1.0; fixed in 4.2.12
- symfony/security-http (Packagist): affected from 4.1.0; fixed in 4.2.12
- symfony/security-http (Packagist): affected from 4.3.0; fixed in 4.3.8
- symfony/security-http (Packagist): affected from 4.3.0; fixed in 4.3.8
- symfony/symfony (Packagist): affected from 4.1.0; fixed in 4.2.12
- symfony/symfony (Packagist): affected from 4.1.0; fixed in 4.2.12
- symfony/symfony (Packagist): affected from 4.3.0; fixed in 4.3.8
- symfony/symfony (Packagist): affected from 4.3.0; fixed in 4.3.8

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-18886/ (Markdown: https://insights.sbomify.com/CVE-2019-18886/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-18886
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-18886
- OSV: https://osv.dev/vulnerability/CVE-2019-18886

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-18886/
Summaries are generated and may contain mistakes; the official description above is the record.