CVE-2025-38086: net: ch9200: fix uninitialised access during mii_nway_restart

Vulnerability summary

CVE-2025-38086 is a medium (CVSS 5.5) Use of Uninitialized Resource vulnerability in debian debian_linux. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 10.6% of scored vulnerabilities.

Timeline

1. 28-06-2025
   PublishedVulnerability first disclosed.
2. 11-05-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: net: ch9200: fix uninitialised access during mii_nway_restart In mii_nway_restart() the code attempts to call mii->mdio_read which is ch9200_mdio_read(). ch9200_mdio_read() utilises a local buffer called "buff", which is initialised with control_read(). However "buff" is conditionally initialised inside control_read(): if (err == size) { memcpy(data, buf, size); } If the condition of "err == size" is not met, then "buff" remains uninitialised. Once this happens the uninitialised "buff" is accessed and returned during ch9200_mdio_read(): return (buff[0] | buff[1] << 8); The problem stems from the fact that ch9200_mdio_read() ignores the return value of control_read(), leading to uinit-access of "buff". To fix this we should check the return value of control_read() and return early on error.

• CWE-908Use of Uninitialized ResourceThe product uses or accesses a resource that has not been initialized.