CVE-2026-68308 Overview
CVE-2026-68308 is a null pointer dereference vulnerability in the Linux kernel's mt76 wireless driver, specifically affecting the mt7996 chipset support code. The flaw exists because the mt76_connac_get_he_phy_cap() routine can theoretically return NULL, but the calling code in the mt7996 driver dereferences the returned cap pointer without validating it first. The upstream Linux kernel maintainers have resolved the issue by adding an explicit pointer check before dereference [CWE-476].
Critical Impact
A NULL return from mt76_connac_get_he_phy_cap() followed by unchecked dereference can trigger a kernel oops, resulting in denial of service on systems using MediaTek MT7996 Wi-Fi hardware.
Affected Products
- Linux kernel builds including the mt76 wireless driver stack
- Systems using the mt7996 MediaTek Wi-Fi 7 chipset driver
- Distributions shipping affected kernel versions prior to the stable backport commits
Discovery Timeline
- 2026-08-10 - CVE-2026-68308 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68308
Vulnerability Analysis
The vulnerability resides in the MediaTek mt76 Wi-Fi driver family, which supports several MediaTek 802.11 chipsets in the Linux kernel. The mt7996 driver invokes mt76_connac_get_he_phy_cap() to obtain a pointer to High Efficiency (HE, Wi-Fi 6) PHY capability data associated with a given band and interface. Downstream code then reads fields from this capability structure to configure or advertise HE features.
As documented in the upstream fix, mt76_connac_get_he_phy_cap() can theoretically return NULL. Prior to the patch, the mt7996 caller did not verify the return value, so a NULL result would cause the kernel to dereference an invalid pointer. This class of defect is a null pointer dereference and typically results in a kernel oops on the affected CPU, terminating the offending kernel thread.
Root Cause
The root cause is a missing return-value check on a helper that may legitimately return NULL. The mt7996 code path treated the pointer as always valid and accessed capability fields directly, violating the defensive programming expectation for helpers that traverse per-interface or per-band capability tables where the requested entry may not exist.
Attack Vector
The advisory does not describe a remote exploitation path or attach a CVSS vector. The condition is a kernel robustness bug reachable through code paths that request HE PHY capabilities on mt7996-based hardware. Successful triggering results in denial of service rather than code execution, as the dereference targets a NULL address and is caught by the kernel's page fault handler. No public proof-of-concept and no known in-the-wild exploitation are associated with this CVE.
The upstream fix, described in the Linux Kernel Commit Fix, adds the missing pointer validation before dereference. Additional backports are tracked in the Linux Kernel Commit Update, Linux Kernel Commit Change, Linux Kernel Commit Patch, and Linux Kernel Commit Improvement.
Detection Methods for CVE-2026-68308
Indicators of Compromise
- Kernel oops or BUG: kernel NULL pointer dereference messages in dmesg referencing symbols in the mt76 or mt7996 modules.
- Unexpected Wi-Fi interface resets or driver panics on hosts using MediaTek MT7996 hardware.
- Repeated crashes correlated with wireless association, scanning, or capability negotiation events.
Detection Strategies
- Inventory Linux endpoints and access points using the mt76 and mt7996 kernel modules by querying lsmod and comparing running kernel versions against upstream stable branches.
- Correlate kernel crash telemetry (kdump, pstore, journal kernel: entries) with the affected module names to identify systems experiencing the null dereference.
- Track kernel package versions in configuration-management data to flag hosts that have not yet received the stable backport.
Monitoring Recommendations
- Forward journalctl -k and /var/log/kern.log entries to a centralized log platform and alert on NULL pointer dereference events referencing mt76* symbols.
- Monitor Wi-Fi interface state transitions and driver reload frequency on affected hardware as a proxy for crash activity.
- Include kernel version and loaded-module inventory in periodic host posture checks.
How to Mitigate CVE-2026-68308
Immediate Actions Required
- Apply the vendor-supplied kernel update for your Linux distribution that incorporates the upstream mt76: mt7996 null-check fix.
- Identify all hosts, embedded devices, and access points using MediaTek MT7996 Wi-Fi hardware and prioritize them for patch deployment.
- Reboot patched systems to load the updated kernel image so the fix takes effect.
Patch Information
The fix adds a pointer check on the value returned by mt76_connac_get_he_phy_cap() before dereferencing it. The primary commit is available at the Linux Kernel Commit Fix, with stable-tree backports tracked across the additional commits linked in the Technical Details section. Consumers should upgrade to a distribution kernel that includes one of these commits rather than cherry-picking manually where possible.
Workarounds
- Where patching is not immediately possible, unload the mt7996 module (modprobe -r mt7996e) on systems that do not require MediaTek MT7996 Wi-Fi connectivity.
- Disable Wi-Fi on affected hosts and rely on wired connectivity until the updated kernel is deployed.
- Restrict physical proximity and untrusted client association on affected access points to reduce exposure to code paths that request HE PHY capabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
