CVE-2026-17545 PHP on Windows: Reserved Device Names Are Not Rejected Before File/Stream I/O which can cause DoS

What is CVE-2026-17545?

CVE-2026-17545 is a medium-severity denial of service vulnerability in Php Php, published on 25 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

On Windows, PHP's filesystem and stream APIs do not reject reserved device names such as CON, PRN, AUX, NUL, COM1 to COM9, LPT1 to LPT9, CONIN$ and CONOUT$ when they appear as a component of a path. An attacker-controlled filename therefore reaches CreateFileW() and opens a device instead of the regular file the application expected, which can block or hang the request and exhaust worker processes.

Weakness: CWE-67

Which versions are affected by CVE-2026-17545?

3 open source packages ship an affected version, including libphp, php and php-min. It affects 1 product.

Products include Php Php.

How do I fix CVE-2026-17545?

Upgrade libphp to a fixed version for your release line: 8.2.34, 8.3.35, 8.4.26 or 8.5.11.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-17545 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-17545 exists.

Other vulnerabilities in Php Php

• CVE-2012-2688 Integer overflow in n/a Critical 10.0
• CVE-2012-2376 Memory corruption in n/a Critical 10.0
• CVE-2011-3268 Memory corruption in n/a Critical 10.0
• CVE-2009-4143 Other in n/a Critical 10.0
• CVE-2008-5557 Memory corruption in n/a Critical 10.0

All Php Php vulnerabilities

Sources

• CVE record
• NVD
• OSV
• How this page is made

Also known as AZL-105141, BIT-libphp-2026-17545, BIT-php-2026-17545, BIT-php-min-2026-17545, MINI-39w4-8p37-7fg8, MINI-3wvm-rghf-5xfc and 7 more.