CVE-2026-23524: Laravel Redis Horizontal Scaling Insecure Deserialization

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 1.0%, percentile 62: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 62% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes laravel/reverb (Composer (PHP)) < 1.7.0, fixed in 1.7.0. Check your lockfile, including transitive dependencies.

What it is

Laravel Reverb provides a real-time WebSocket communication backend for Laravel applications. In versions 1.6.3 and below, Reverb passes data from the Redis channel directly into PHP’s unserialize() function without restricting which classes can be instantiated, which leaves users vulnerable to Remote Code Execution. The exploitability of this vulnerability is increased because Redis servers are commonly deployed without authentication, but only affects Laravel Reverb when horizontal scaling is enabled (REVERBSCALINGENABLED=true). This issue has been fixed in version 1.7.0. As a workaround, require a strong password for Redis access and ensure the service is only accessible via a private network or local loopback, and/or set REVERBSCALINGENABLED=false to bypass the vulnerable logic entirely (if the environment uses only one Reverb node).

From the GitHub advisory

Impact

This vulnerability affects Laravel Reverb versions prior to v1.7.0 when horizontal scaling is enabled (REVERBSCALINGENABLED=true).

The exploitability of this vulnerability is increased because Redis servers are commonly deployed without authentication.

With horizontal scaling enabled, Reverb servers communicate via Redis PubSub. Reverb previously passed data from the Redis channel directly into PHP’s unserialize() function without restricting which classes could be instantiated.

Risk: Remote Code Execution (RCE)

Weakness type: CWE-502.

Product: laravel/reverb (Composer (PHP)) · Assigned by: GitHub_M · Published: 2026-01-21

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.98% probability of exploitation activity in the next 30 days; percentile 62.

Timeline

• 2026-01-21 — CVE record published by GitHub_M
• 2026-01-21 — GitHub-reviewed advisory GHSA-m27r-m6rx-mhm4 published (critical)
• 2026-01-22 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-m27r-m6rx-mhm4 github.com
2. CVE.org record CVE-2026-23524 cve.org
3. NVD entry CVE-2026-23524 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. cwe.mitre.org cwe.mitre.org
4. github.com github.com
5. laravel.com laravel.com
6. laravel.com laravel.com

Critical Composer (PHP) advisories · Today’s Security Digest