CVE-2026-82416 (CVSS 7.7)

Description

FrankenPHP is a modern application server for PHP. Prior to 1.12.5, FrankenPHP worker mode can retain PHP session state between requests when the session extension is loaded as a shared module and is unavailable through HAVE_PHP_SESSION at compile time. In this build configuration, frankenphp_reset_session_state() is compiled out, PS(id) can survive a request boundary, and a subsequent session_start() can ignore the new request's cookie because an identifier is already present. Under concurrent requests, session_id() can therefore return another client's identifier or a stale identifier from a previous request on the same worker thread, causing cross-user session exposure, possible session hijacking, and intermittent logout behavior. Builds with the session extension statically linked, including the official static binaries and Docker images, are not affected. This issue is fixed in version 1.12.5.

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CVSS v3.1 Score

7.7

HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

EPSS — Exploit Prediction

0.0023

Probability of exploitation

0.13%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-362 CWE-362

CWE-488 CWE-488

References

Other References

https://github.com/php/frankenphp/commit/be24d82531675f90862b8cde1e9fc7e9ee855aa5 https://github.com/php/frankenphp/pull/2523 https://github.com/php/frankenphp/releases/tag/caddy/v1.12.5 https://github.com/php/frankenphp/security/advisories/GHSA-v3ph-cgqh-r8p5

Frequently Asked Questions

What is CVE-2026-82416? +

FrankenPHP is a modern application server for PHP. Prior to 1.12.5, FrankenPHP worker mode can retain PHP session state between requests when the session extension is loaded as a shared module and is unavailable through HAVE_PHP_SESSION at compile time. In this build configuration, frankenphp_reset_session_state() is compiled out, PS(id) can survive a request boundary, and a subsequent session_start() can ignore the new request's cookie because an identifier is already present. Under concurrent requests, session_id() can therefore return another client's identifier or a stale identifier from a previous request on the same worker thread, causing cross-user session exposure, possible session hijacking, and intermittent logout behavior. Builds with the session extension statically linked, including the official static binaries and Docker images, are not affected. This issue is fixed in version 1.12.5. It has a CVSS v3.1 base score of 7.7 (HIGH).

How severe is CVE-2026-82416? +

CVE-2026-82416 has a CVSS v3.1 score of 7.7 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0023, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-82416? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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