Vulnerability · Published Sep 25, 2026 · Assigned by php
CVE-2026-17545PHP on Windows: Reserved Device Names Are Not Rejected Before File/Stream I/O which can cause DoS
Medium 6.9
In plain English
A medium-severity security flaw in PHP from PHP Group. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities).
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:22.04:LTS | php8.1 | no fix listed | UBUNTU-CVE-2026-17545 |
| Ubuntu:24.04:LTS | php8.3 | no fix listed | UBUNTU-CVE-2026-17545 |
| Ubuntu:26.04:LTS | php8.5 | no fix listed | UBUNTU-CVE-2026-17545 |
Affected products (as reported)
Weakness: CWE-67 · Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:H