A newly disclosed high-severity vulnerability in the Laravel PHP framework exposes web applications to CRLF injection attacks through the framework’s built-in email validation logic.
Potentially enabling unauthenticated attackers to manipulate outbound mail content, redirect messages to unintended recipients, and abuse the application’s mail infrastructure for phishing or spam relay.
The flaw, tracked as CVE-2026-48019 and assigned GHSA-5vg9-5847-vvmq, was published two days ago by researcher andrei-laravel and credited to security researcher OmarXtream.
CRLF stands for Carriage Return (\r, ASCII 13) and Line Feed (\n, ASCII 10) two control characters used in text-based protocols to denote line breaks.
In a CRLF injection attack, an adversary supplies specially crafted input containing these characters to manipulate how an application processes headers, responses, or protocol-level messages.
This class of vulnerability is cataloged under CWE-93: Improper Neutralization of CRLF Sequences, and it can enable HTTP response splitting, log injection, web cache poisoning, and, as in this case, email header manipulation.
The Laravel vulnerability specifically arises at the intersection of three components: Laravel’s own email validation layer, Symfony Mailer, and Symfony MIME.
When a Laravel application accepts a user-supplied email address in registration flows, contact forms, or notification endpoints and passes it downstream to Symfony’s mail transport without adequate sanitization, CRLF sequences embedded in that address can bleed into the SMTP message structure.
According to the official advisory, this combination “may allow an unauthenticated attacker to interfere with outbound email processing in applications that send mail to user-supplied addresses.”
The attack vector is entirely network-based, requires no authentication, and demands no user interaction making this a particularly dangerous bug profile. An attacker targeting a vulnerable Laravel application only needs access to an input field that accepts an email address.
By injecting a payload such as victim@example.com\r\nBcc: attacker@evil.com, the CRLF sequence causes the mail parser to interpret the second line as a new SMTP header.
Because Symfony MIME processes certain character sequences in ways that do not fully neutralize injected line breaks before they reach the transport layer, the injected header survives into the outbound message. The consequences include:
- Content manipulation — altering the body or subject of outgoing application emails
- Mail relay abuse — routing emails to attacker-controlled addresses using the application’s authenticated SMTP session
- Phishing facilitation — using the organization’s trusted domain infrastructure to send fraudulent messages to targets
- Unauthorized access exposure — intercepting transactional emails such as password reset links or OTP tokens
The CVSS v3.1 vector for this vulnerability is CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L, yielding a base score of 8.9. While attack complexity is rated High, reflecting that exploitation requires a precise understanding of the mail pipeline.
The absence of required privileges, and the Changed scope make successful exploitation highly impactful across Confidentiality and Integrity dimensions.
Affected Versions
All Laravel applications running the following versions of laravel/framework (Composer package) are vulnerable:
- Laravel 13.x — All versions <= 13.9.0
- Laravel 12.x — All versions < 12.60.0
Applications on older, unsupported Laravel branches (Laravel 10, 11) should also be evaluated, as they may carry similar unpatched behaviors in email handling logic and lack upstream security backports.
Patched Versions
The Laravel maintainers have released patched versions that introduce the necessary CRLF filtering at the email validation layer before input reaches the Symfony Mailer transport. Developers must upgrade to one of the following versions immediately:
- Laravel 13.x → Upgrade to
>= 13.10.0 - Laravel 12.x → Upgrade to
>= 12.60.0
Update using Composer with the following command:
composer update laravel/frameworkBeyond patching, security teams should implement these hardening measures:
- Strip control characters — Apply
preg_replace('/[\r\n]/', '', $email)before passing any user-supplied email to mail functions - Strict input validation — Use Laravel’s
validate()withemail:rfc,dnsrules and reject inputs containing encoded CRLF sequences (%0d,%0a) - WAF rules — Deploy Web Application Firewall rules that strip
\r\nand their URL-encoded equivalents from all inbound parameters - Audit contact forms and auth flows — Review all endpoints where user-supplied addresses are passed to
Mail::to(),Mail::cc(),Mail::bcc(), orNotification::route() - Structured logging — Adopt JSON-based logging to prevent CRLF from corrupting log integrity alongside mail security hardening
The scope of this vulnerability is rated Changed in CVSS terms, meaning the impact extends beyond the vulnerable component itself in this case, the Laravel application and affects the downstream mail infrastructure.
Organizations relying on shared SMTP relays, cloud-based transactional email providers (SendGrid, Mailgun, Amazon SES), or on-premise mail servers are at risk of having their sending reputation damaged if their Laravel applications are weaponized as spam or phishing relays.
The severity depends heavily on what the application sends via email. Applications that transmit password reset tokens, two-factor authentication codes, or financial notifications are at elevated risk of confidentiality breach if attackers can redirect or copy outbound messages.
OWASP classifies CRLF injection as a high-risk control failure under its injection category, and the Laravel ecosystem’s broad deployment footprint powering millions of applications worldwide amplifies the aggregate risk surface.
| Attribute | Detail |
|---|---|
| CVE ID | CVE-2026-48019 |
| GHSA ID | GHSA-5vg9-5847-vvmq |
| Package | laravel/framework (Composer) |
| CWE | CWE-93 – CRLF Injection |
| CVSS Score | 8.9 (High) |
| Attack Vector | Network |
| Auth Required | None |
| Patched Versions | ≥ 13.10.0 / ≥ 12.60.0 |
| Researcher | OmarXtream |
Security teams should monitor logs and mail server records for the following patterns indicative of active exploitation attempts:
- Email address fields containing
%0d%0a,\r\n,%0a, or%0dcharacter sequences - Unexpected
Bcc:,Cc:, orX-Custom-Header:fields in outbound SMTP logs not generated by application logic - Anomalous spikes in outbound email volume from application mail accounts
- SMTP authentication logs showing bulk delivery to external domains not matching the application’s intended recipient list
FAQ
Q1. What is CVE-2026-48019?
It is a high-severity CRLF injection vulnerability (CVSS 8.9) in Laravel’s email validation layer that allows unauthenticated attackers to manipulate outbound email content and abuse mail relay infrastructure.
Q2. Which Laravel versions are affected by this CRLF injection flaw?
All Laravel 13.x versions up to and including 13.9.0 and all Laravel 12.x versions below 12.60.0 are vulnerable to CVE-2026-48019.
Q3. How can developers fix the CVE-2026-48019 vulnerability?
Upgrade to Laravel 13.10.0 or 12.60.0 via composer update laravel/framework and strip CRLF characters from all user-supplied email addresses before passing them to mail functions.
Q4. Can a WAF block CRLF injection attacks against Laravel applications?
Yes, deploying a WAF with rules that filter \r\n, %0d%0a, and related encoded variants from input parameters provides an effective mitigation layer while patch deployment is in progress.
Site: thecybrdef.com
For more insights and updates, follow us on Google News, Twitter, and LinkedIn.
About the Author
