CVE-2025-48951: Auth0-PHP SDK Deserialization of Untrusted Data vulnerability

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 0.7%, percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% 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 auth0/auth0-php (Composer (PHP)) >= 8.0.0-BETA3, < 8.3.1, fixed in 8.3.1. Check your lockfile, including transitive dependencies.

What it is

Auth0-PHP is a PHP SDK for Auth0 Authentication and Management APIs. Versions 8.0.0-BETA3 prior to 8.3.1 contain a vulnerability due to insecure deserialization of cookie data. If exploited, since SDKs process cookie content without prior authentication, a threat actor could send a specially crafted cookie containing malicious serialized data. Applications using the Auth0-PHP SDK are affected, as are applications using the Auth0/symfony, Auth0/laravel-auth0, or Auth0/wordpress SDKs, because those SDKsrely on the Auth0-PHP SDK versions from 8.0.0-BETA3 until 8.14.0. Version 8.3.1 contains a patch for the issue.

From the GitHub advisory

Overview The Auth0 PHP SDK contains a vulnerability due to insecure deserialization of cookie data. If exploited, since SDKs process cookie content without prior authentication, a threat actor could send a specially crafted cookie containing malicious serialized data.

Am I Affected? You are affected by this vulnerability if you meet the following preconditions:

1. Applications using the Auth0-PHP SDK, versions between 8.0.0-BETA3 to 8.3.0. 2. Applications using the following SDKs that rely on the Auth0-PHP SDK versions between 8.0.0-BETA3 to 8.3.0: a. Auth0/symfony, b. Auth0/laravel-auth0, c. Auth0/wordpress.

Fix Upgrade Auth0/Auth0-PHP to 8.3.1.

Acknowledgement Okta would like to thank Andreas Forsblom for discovering this vulnerability.

Weakness type: CWE-502.

Product: auth0/auth0-php (Composer (PHP)) · Assigned by: GitHub_M · Published: 2025-06-03

Affected and fixed versions

Severity scores

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

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 partial.
• FIRST EPSS (model of 2026-10-21): 0.75% probability of exploitation activity in the next 30 days; percentile 54.

Timeline

• 2025-06-03 — CVE record published by GitHub_M
• 2025-06-04 — CVE record last updated
• 2025-06-04 — GitHub-reviewed advisory GHSA-v9m8-9xxp-q492 published (critical)

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-v9m8-9xxp-q492 github.com
2. CVE.org record CVE-2025-48951 cve.org
3. NVD entry CVE-2025-48951 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. github.com github.com

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