CVE-2026-68412 Overview
CVE-2026-68412 is a memory leak vulnerability in the Linux kernel's cfg80211 wireless configuration subsystem. The flaw resides in the cfg80211_wext_siwscan() function, which processes wireless scan requests through the legacy Wireless Extensions (WEXT) interface. When a scan request contains an SSID exceeding IEEE80211_MAX_SSID_LEN, the function returns an error without freeing the previously allocated creq buffer. This results in kernel memory being leaked on each failed request.
Critical Impact
Repeated triggering of the error path leaks kernel heap memory, which can degrade system stability over time and contribute to resource exhaustion on long-running Linux systems using wireless interfaces.
Affected Products
- Linux kernel versions containing the cfg80211_wext_siwscan() function prior to the patch
- Distributions shipping affected stable kernel branches
- Systems using WEXT-based wireless scanning through cfg80211
Discovery Timeline
- 2026-08-10 - CVE-2026-68412 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68412
Vulnerability Analysis
The vulnerability affects the cfg80211_wext_siwscan() function in the Linux kernel wireless subsystem. This function handles SIOCSIWSCAN ioctl requests issued by userspace to initiate wireless network scans via the legacy Wireless Extensions API. During request processing, the kernel allocates a cfg80211_scan_request structure referenced by the local pointer creq.
The function then validates each supplied SSID length against the IEEE80211_MAX_SSID_LEN constant. If the validation fails, the function returns an error directly rather than routing execution through the shared cleanup path. The allocated creq memory is never freed on this branch, producing a kernel-space memory leak [CWE-401].
The upstream fix redirects the failure branch to the existing error handling label so that creq is released before the function returns. Three kernel commits address the issue across stable branches: 99d2e850c643, c6659f66d4ee, and e67dc2b8d5ac.
Root Cause
The root cause is an incomplete error handling path. Standard kernel coding practice requires all failure branches after resource allocation to jump to a unified cleanup label. The SSID length check bypassed this convention and returned directly, orphaning the creq allocation on the kernel heap.
Attack Vector
A local user with permission to submit wireless scan requests can trigger the leak by issuing SIOCSIWSCAN ioctls containing an oversized SSID field. Each rejected request leaks the associated scan-request structure. Sustained triggering can pressure kernel memory over time. The vulnerability does not enable code execution or privilege escalation on its own.
No verified public exploitation code exists for this issue. See the Git Kernel Patch for the reference implementation of the fix.
Detection Methods for CVE-2026-68412
Indicators of Compromise
- Unexplained growth in kernel slab allocations tied to cfg80211 scan request structures
- Repeated SIOCSIWSCAN ioctl calls from unprivileged processes that fail with -EINVAL
- Wireless daemons or utilities issuing malformed scan requests with SSID length greater than 32 bytes
Detection Strategies
- Audit kernel version strings across the Linux fleet and compare against the patched stable branches referenced in the kernel.org commits
- Monitor /proc/slabinfo for abnormal growth in kmalloc caches associated with wireless scanning
- Use auditd rules to capture ioctl syscalls targeting wireless interfaces with anomalous argument patterns
Monitoring Recommendations
- Track kernel memory usage trends on wireless-enabled hosts, particularly access points and long-running Linux endpoints
- Alert on wireless drivers or userspace tools generating repeated failed scan requests
- Correlate kernel warnings and OOM events with wireless subsystem activity in centralized logging
How to Mitigate CVE-2026-68412
Immediate Actions Required
- Apply the upstream Linux kernel patches referenced in commits 99d2e850c643, c6659f66d4ee, and e67dc2b8d5ac
- Update to a distribution kernel that incorporates the fix on affected stable branches
- Restart affected systems after patching to load the corrected kernel image
Patch Information
The fix is available in the mainline and stable Linux kernel trees. See the Git Kernel Patch, the Git Kernel Patch, and the Git Kernel Patch for the corresponding commits. Distribution vendors typically backport these patches to supported stable kernel series.
Workarounds
- Restrict local user access on hosts where kernel updates cannot be immediately applied
- Disable legacy Wireless Extensions where modern nl80211 interfaces are available and sufficient
- Reboot long-running wireless hosts periodically to reclaim any leaked kernel memory until patching is complete
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
