CVE-2025-39957: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-39957 is a vulnerability discovered in the Linux kernel's mac80211 wireless networking subsystem, disclosed on October 9, 2025. The issue specifically affects the handling of S1G (Sub-1GHz) capability elements in wireless scanning functionality (NVD).

The vulnerability stems from a buffer length validation issue where the S1G capability element is not properly accounted for in the scan_ies_len calculation within the ieee80211_prep_hw_scan() function. This oversight leads to a validation failure and subsequent WARN condition in __ieee80211_start_scan(). The vulnerability has been assigned a CVSS v3.1 base score of 4.5 with vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L (Red Hat).

The primary impact of this vulnerability is the disruption of hardware scanning functionality in affected systems. When triggered, the vulnerability prevents hardware wireless scanning from functioning properly, potentially affecting network discovery and connectivity capabilities (NVD).

As a temporary workaround, systems can prevent the mac80211 module from being loaded. This can be accomplished by blacklisting the kernel module to prevent automatic loading. For a permanent fix, the scan_ies_len calculation has been modified to properly accommodate the S1G capability length (Red Hat).