SymfonyFramework / library · Sensiolabs
CVE-2019-18886
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceSymfony's security component had a user enumeration vulnerability in the switch user functionality. The application returned different responses when attempting to switch to existing versus non-existing users, allowing attackers to discover valid usernames through repeated unauthenticated or unauthorized requests.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
SymfonyFramework / library
>= 4.2.0, <= 4.2.11>= 4.3.0, <= 4.3.7CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check Symfony framework versionRun `composer show symfony/symfony 2>/dev/null | grep version` or check your composer.lock file for the symfony/symfony package versionAffected if The installed version is >= 4.2.0 and <= 4.2.11, or >= 4.3.0 and <= 4.3.7
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Verify switch user feature is enabledInspect your application's security configuration file (config/packages/security.yaml or app/config/config.yml) and look for the switch_user setting under your firewall configurationAffected if The switch_user option is set to true or configured with a provider under any firewall entry
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Confirm user provider is configuredCheck the security configuration for a user provider (property: or entity: or another provider type) that the switch user feature would useAffected if A user provider is configured and the switch_user feature is active, allowing the application to query user existence
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Test response consistency (if direct testing is authorized)Make two GET requests to the switch user endpoint (typically ?_switch_user=EXISTING_USER and ?_switch_user=NONEXISTENT_USER) and compare the HTTP response codes or error messagesAffected if The application returns different responses (such as a 302 redirect for existing users versus a 404 or error for non-existing users), confirming the enumeration vulnerability is present
You are affected if your Symfony version falls within 4.2.0-4.2.11 or 4.3.0-4.3.7 AND the switch_user feature is enabled in your security configuration.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to Symfony 4.2.12, 4.3.8, or later versions where the user existence check was made consistent, or implement rate limiting on the switch user endpoint to prevent enumeration attacks.
Fix this in Symfony
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-18886 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2019-18886 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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