SymfonyFramework / library · Sensiolabs
CVE-2026-45063
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 · uneditedSymfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, X509Authenticator extracts the user identifier from $_SERVER['SSL_CLIENT_S_DN'] with an unanchored regex that matches emailAddress= anywhere in the distinguished name, allowing an attacker with a trusted certificate containing emailAddress=victim inside another RDN value such as CN to authenticate as the victim. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.
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 confidenceThe X509Authenticator in Symfony uses an unanchored regex to extract user identifiers from the SSL_CLIENT_S_DN environment variable. Because the regex matches emailAddress= anywhere in the distinguished name string rather than only in the proper emailAddress field, an attacker with a trusted certificate containing emailAddress=victim embedded within another RDN (like CN) can trick the authenticator into extracting and using the victim's identity for authentication.
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
< 5.4.52>= 6.0.0, < 6.4.40>= 7.0.0, < 7.4.12>= 8.0.0, < 8.0.12CVSS 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
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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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Identify Symfony installation versionRun `composer show symfony/framework-bundle` or check your `composer.lock` for the installed Symfony versionAffected if The version is less than 5.4.52, or between 6.0.0 and 6.4.40 (exclusive), between 7.0.0 and 7.4.12 (exclusive), or between 8.0.0 and 8.0.12 (exclusive)
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Confirm X509Authenticator is in useSearch your Symfony security configuration files (typically `config/packages/security.yaml`) for `x509` authenticator entries under `security.firewalls`Affected if An X509 authenticator firewall is configured and actively handling authentication requests
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Verify SSL_CLIENT_S_DN is processedCheck your environment or server configuration to confirm the SSL_CLIENT_S_DN environment variable is being passed to the application (common in web server configs for client certificates)Affected if SSL_CLIENT_S_DN is populated and used by the application for authentication
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Inspect user identifier extraction logicReview the X509Authenticator source code or its regex pattern used to extract the user identifier from SSL_CLIENT_S_DN; look for patterns matching emailAddress= without proper DN field position validationAffected if The regex uses an unanchored pattern that matches emailAddress= anywhere in the DN string rather than only within the emailAddress field specifically
You are affected if your Symfony version is vulnerable AND the X509Authenticator is configured to use SSL_CLIENT_S_DN with an unanchored regex that can match emailAddress values outside the proper DN field.
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.
dbcve · scoped5.4.526.4.407.4.12
Upgrade Symfony to version 5.4.52, 6.4.40, 7.4.12, or 8.0.12, which contain the fix that properly validates the emailAddress field position in the distinguished name.
Upgrade to Symfony 5.4.52, 6.4.40, 7.4.12, or 8.0.12 (minimum fixed version for your current major branch)
- 1. Identify the current Symfony version by running `composer show symfony/framework-bundle` or checking composer.lock
- 2. Review the Symfony upgrade guide for your current major version (e.g., 5.4 to 5.4, 6.x to 6.4, 7.x to 7.4, or 8.x to 8.0)
- 3. Update the Symfony version constraint in composer.json: for 5.4.x use ^5.4.52, for 6.x use ^6.4.40, for 7.x use ^7.4.12, or for 8.x use ^8.0.12
- 4. Run `composer update symfony/framework-bundle symfony/security-bundle --with-dependencies` to update the packages
- 5. Clear the Symfony cache with `php bin/console cache:clear` or `php bin/console cache:clear --env=prod`
- 6. Verify the fix by checking that the X509Authenticator now uses an anchored regex for emailAddress matching in the vendor source
- 7. Test the authentication flow with test certificates to confirm the vulnerability is remediated
- 8. Deploy to production after thorough testing
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Symfony
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-45063 — 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-2026-45063 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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