SymfonyFramework / library · Sensiolabs
CVE-2026-45070
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, Symfony\Component\Mime\Header\ParameterizedHeader validates and encodes parameter values but emits parameter names verbatim, allowing a caller that derives a parameter name from untrusted input to include CRLF or other non-token bytes and inject additional headers into rendered structured mail headers such as Content-Type or Content-Disposition. This issue is reported as 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 confidenceIn Symfony's Mime component, the ParameterizedHeader class validates and encodes parameter values but outputs parameter names verbatim without validation. This allows attackers to inject CRLF sequences or other non-token bytes into parameter names, enabling injection of arbitrary email headers in Content-Type or Content-Disposition headers.
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
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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 installed Symfony Mime versionRun 'composer show symfony/mime' or inspect your composer.lock for the symfony/mime package versionAffected if Version is < 5.4.52, or >= 6.0.0 and < 6.4.40, or >= 7.0.0 and < 7.4.12, or >= 8.0.0 and < 8.0.12
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Locate ParameterizedHeader usage in codebaseSearch source code for 'ParameterizedHeader' class instantiation or calls to header methods that set Content-Type or Content-Disposition parameters (e.g., Content-Disposition: attachment; filename*=...)Affected if Code passes user-supplied or unvalidated input as parameter names to email headers
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Identify email header generation from untrusted sourcesReview code that builds email messages using Symfony Mime, looking for scenarios where request parameters, user inputs, or database values influence parameter names in Content-Type or Content-Disposition headersAffected if Untrusted input can reach parameter name arguments in email header methods
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Inspect email sending workflowsTrace the flow from user input to Symfony Mailer message construction, checking if input validation exists before setting header parametersAffected if No input validation is performed on parameter names before they are used in email headers
You are affected if your Symfony Mime version falls within the affected ranges AND your application passes untrusted input as parameter names to Content-Type or Content-Disposition headers.
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, 8.0.12 or later. If immediate patching is not possible, audit code that uses Symfony's Mime component and ensure untrusted input cannot influence parameter names in email headers.
5.4.52, 6.4.40, 7.4.12, or 8.0.12 (select based on your current major version)
- Run `composer require symfony/symfony:^5.4.52` to upgrade to the 5.4.x fixed release, or
- Run `composer require symfony/symfony:^6.4.40` to upgrade to the 6.4.x fixed release, or
- Run `composer require symfony/symfony:^7.4.12` to upgrade to the 7.4.x fixed release, or
- Run `composer require symfony/symfony:^8.0.12` to upgrade to the 8.0.x fixed release, depending on your current major version branch
- Run `composer update symfony/symfony` to apply the changes
- Verify the upgrade by running your test suite
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
- 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 $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-45070 — 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-2026-45070 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
- No spam, self-promotion, credentials, or personal data