CVE-2026-17545: PHP on Windows: Reserved Device Names Are Not Rejected Before File/Stream I/O which can cause DoS
Fixed (Reserved device names are not rejected before file and stream I/O). (CVE-2026-17545)
Other sources
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.
— MITRE
PHP on Windows: Reserved Device Names Are Not Rejected Before File/Stream I/O which can cause DoS
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 8.4.26 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 8.3.35-1