Laravel CRLF Injection Vulnerability Can Interfere With Outbound Email Processing

A high-severity Laravel vulnerability can let unauthenticated attackers interfere with outbound email processing in certain applications that send messages to user-supplied email addresses.

The flaw, tracked as CVE-2026-48019 and disclosed in a GitHub security advisory, affects laravel/framework 12.x versions before 12.60.0 and 13.x versions up to 13.9.0. Laravel maintainers fixed the issue in versions 12.60.0 and 13.10.0.

The vulnerability involves CRLF injection in Laravel’s default email validation rule. In some mail workflows, a crafted email address can reach the mail transport layer and influence how an outbound message gets processed.

What CVE-2026-48019 means for Laravel apps

CRLF stands for carriage return and line feed. Email systems and many internet protocols use these characters to separate headers, lines, and message parts.

When an application fails to neutralize CRLF characters in user-controlled input, attackers may inject extra structure into a message. In this case, the vulnerable path involves Laravel email validation combined with how Symfony Mailer and Symfony Mime handle certain character sequences.

The CERT-FR notice describes the issue as a Laravel vulnerability that can allow a security policy bypass. That broad wording reflects the main risk: an attacker may cause outbound email to behave in ways the application developer did not intend.

Detail	Information
CVE	CVE-2026-48019
Package	laravel/framework
Affected versions	12.x before 12.60.0 and 13.x up to 13.9.0
Fixed versions	12.60.0 and 13.10.0 or later
Severity	High, CVSS 8.9
Weakness	CWE-93, improper neutralization of CRLF sequences
Main impact	Outbound email manipulation, unintended delivery, and possible mail relay abuse

How the Laravel CRLF issue can affect email workflows

The vulnerable scenario matters most when an application accepts an email address from a user and then sends mail to that address. Common examples include account registration, password resets, contact forms, invite flows, email verification, and support notifications.

Laravel’s mail documentation shows how applications can build and send mail through Laravel’s mail system. Many production apps combine this mail layer with user-supplied recipient addresses from forms or account records.

If the email input contains malicious CRLF sequences and reaches the mail layer under the right conditions, the attacker may influence message content, cause delivery to unintended recipients, or trigger unintended email transmissions.

Why Symfony Mailer and Symfony Mime matter

Laravel uses Symfony components for mail and message handling. The security advisory specifically mentions the interaction between Laravel email validation and how Symfony Mailer and Symfony Mime handle certain character sequences.

The Symfony Mailer documentation explains how Symfony handles email delivery through different transports. That makes the mail transport layer an important part of the attack path when malformed addresses reach it.

This does not mean Symfony Mailer itself created the Laravel vulnerability. The advisory points to Laravel’s email validation behavior in combination with downstream mail handling. Developers should patch Laravel instead of trying to work around the issue only at the mail server level.

What attackers could try to do

The advisory says an unauthenticated attacker may interfere with outbound email processing. Attack complexity is high, but the attacker does not need an account or user interaction.

A successful attack could affect confidentiality and integrity. For example, an attacker may try to influence emails that contain account links, tokens, notifications, or sensitive operational details.

The Cybersecurity Help database summarizes the issue as a remote flaw that may influence sent email content, cause delivery to unintended recipients, or cause the mail server to send unintended messages.

Possible impact	What it means in practice	Risk level
Unintended recipients	A crafted address may affect where outbound email gets delivered.	High for apps that send sensitive links or data by email
Mail content manipulation	Attackers may influence parts of an outbound message under certain conditions.	High if emails contain tokens or workflow approvals
Mail relay abuse	The application’s mail infrastructure may send unintended messages.	High for public forms and high-volume mailers
Reputation damage	Abused mail systems may trigger blocklists or trust issues.	Medium to high depending on mail volume
Availability impact	Mail processing may face disruption or abuse.	Low in the CVSS vector

Which Laravel applications face the most risk

Apps with public forms that trigger email are the clearest concern. These include password reset forms, “invite user” forms, contact forms, quote request pages, onboarding workflows, and email verification screens.

Laravel’s validation documentation shows how applications commonly validate incoming request data before continuing normal execution. CVE-2026-48019 highlights why validation rules that appear routine can still have security impact when their output flows into downstream systems.

Applications that never send mail to user-supplied addresses face lower practical exposure. Still, teams should patch affected Laravel versions because future code changes, packages, or background jobs may introduce a vulnerable mail path later.

Why this is classified as CWE-93

The weakness category is CWE-93, which covers improper neutralization of CRLF sequences. This class of bug appears when software treats CRLF as a special separator but fails to filter or quote those characters in user-controlled input.

In email processing, CRLF is sensitive because headers and message bodies use line boundaries. If an attacker can inject unexpected line breaks, they may alter how a downstream mail component interprets the message.

This is why developers should not treat email validation only as a format check. They should also consider where the value goes next, especially when the value becomes part of a mail envelope, header, or transport-level message.

How developers should patch and reduce risk

The primary fix is to update laravel/framework to 12.60.0 or later, or 13.10.0 or later. Teams should prioritize public-facing apps that use untrusted email input in mail workflows.

The Laravel maintainers’ advisory says affected applications may face unauthorized access and mail relay abuse, with severity depending on what the application sends by email and how the mail infrastructure is configured.

Developers should also review custom validation rules, mail helper functions, notification classes, queued mail jobs, contact-form handlers, and third-party packages that pass user-controlled email values into the mail system.

• Upgrade Laravel 12.x applications to 12.60.0 or later.
• Upgrade Laravel 13.x applications to 13.10.0 or later.
• Review all forms that accept email addresses and trigger outbound mail.
• Check password reset, registration, invitation, support, and contact workflows.
• Reject CRLF characters in email fields at the application edge.
• Review queued mail jobs that may process older stored email values.
• Monitor mail logs for unexpected recipients, abnormal headers, and unusual volume spikes.
• Review mail provider dashboards for blocklist, bounce, and abuse signals.

Operational signs teams should investigate

There are no universal indicators of compromise for this vulnerability because the attack depends on how each application handles mail. Instead, teams should inspect mail logs, application logs, queue logs, and mail provider analytics.

Useful warning signs include unexpected recipients, unusual header patterns, repeated failed email validation attempts, spikes in outbound mail, unusual bounce messages, and password reset emails sent to unexpected destinations.

The CERT-FR advisory recommends referring to the vendor bulletin for fixes. That means patching should come first, followed by a focused review of email workflows that accepted untrusted input before the update.

Area to review	What to look for	Why it matters
Application logs	Email fields containing encoded or raw line-break characters	May indicate attempted CRLF injection
Mail logs	Unexpected recipients, copied users, or unusual delivery paths	Can show outbound mail manipulation
Queue workers	Failed mail jobs or repeated retries tied to unusual addresses	May reveal malformed payloads reaching mail code
Password reset flow	Reset emails sent to unexpected recipients or domains	Could expose account recovery links
Mail provider dashboard	Volume spikes, blocklist alerts, abuse reports, or bounce spikes	Can indicate relay abuse or reputation damage

Security teams should review mail trust boundaries

Email often crosses several trust boundaries. A value may start in a public form, pass through Laravel validation, enter an event or notification class, move into a queued job, and then reach an external mail provider.

The Symfony Mailer guidance shows how mail systems use transports to send messages through services such as SMTP and API-based providers. That downstream dependency makes strict input handling important before the application hands values to the mail layer.

Laravel’s mail guide also shows that modern apps can build complex messages with envelopes, content, attachments, and recipients. Any app that turns public input into mail metadata should treat that path as security-sensitive.

Best practices after applying the update

After updating, developers should run automated tests for registration, password resets, contact forms, and any custom notification flow. They should include malicious email strings with carriage returns, line feeds, encoded CRLF, and unusual Unicode characters.

Teams should also review the Laravel validation docs for recommended validation patterns and make sure email fields combine framework validation with application-level business rules.

The Cybersecurity Help entry notes that no public exploit was listed at publication time. That can change quickly, so teams should not delay patching because exploit code has not appeared publicly.

Bottom line for Laravel developers

CVE-2026-48019 is a high-severity issue because email often carries account links, security notifications, support messages, and transactional content. If attackers can interfere with that channel, they may reach sensitive workflows without directly compromising the application server.

The fix is available in Laravel 12.60.0 and 13.10.0. Developers should update first, then review any code path that accepts an email address from users and sends mail based on that value.

The broader lesson matches CWE-93 guidance: user-controlled line separators must not reach downstream components that treat CRLF as structure. In mail workflows, that rule protects both users and the organization’s email infrastructure.

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