CVE-2026-53257 Overview
CVE-2026-53257 affects the Linux kernel cfg80211 wireless subsystem. The vulnerability stems from inconsistent handling of High Efficiency (HE) and Extremely High Throughput (EHT) Wi-Fi capability elements. When eht_cap is set but eht_oper is missing, mac80211 can crash during processing. Researcher Xiang Mei reported the issue, leading to a kernel patch that enforces consistency between HE and EHT capability and operation elements. The fix prevents downstream code paths from dereferencing partial or mismatched configuration state. The flaw is categorized as a denial-of-service condition affecting kernels with Wi-Fi 7 (EHT) support enabled.
Critical Impact
A malformed or crafted set of Wi-Fi capability elements can trigger a kernel crash in mac80211, resulting in denial of service on affected Linux systems with cfg80211/mac80211 Wi-Fi stacks.
Affected Products
- Linux kernel — cfg80211 and mac80211 wireless subsystems
- Kernel branches prior to the commits referenced in the upstream stable tree
- Distributions shipping affected kernel versions with EHT (Wi-Fi 7) support
Discovery Timeline
- 2026-06-25 - CVE-2026-53257 published to NVD
- 2026-06-25 - Last updated in NVD database
Technical Details for CVE-2026-53257
Vulnerability Analysis
The defect resides in the cfg80211 subsystem, which manages Wi-Fi configuration for the Linux kernel. The companion mac80211 layer consumes the capability data that cfg80211 accepts and parses. EHT defines Wi-Fi 7 PHY and MAC behavior and is paired with HE (Wi-Fi 6) capability and operation information elements. The kernel expects both the capability element (eht_cap) and the operation element (eht_oper) to be present together. When only the capability element exists, mac80211 proceeds with logic that assumes the operation element is available, leading to a crash. The upstream fix enforces consistency at the cfg80211 layer rather than patching each downstream consumer. The change rejects configurations where HE or EHT capability and operation elements are not provided as a consistent pair.
Root Cause
The root cause is missing input validation between paired Wi-Fi information elements. cfg80211 previously accepted asymmetric combinations of HE/EHT capability and operation data. Downstream mac80211 code assumed symmetry without rechecking, producing a kernel null pointer dereference or similar fault. This is a classic improper input validation flaw at a subsystem boundary.
Attack Vector
An attacker capable of supplying crafted Wi-Fi management frames or capability data to a vulnerable host can drive cfg80211 into the inconsistent state. The exploitation surface depends on the device role, including station, access point, and mesh configurations. The result is a kernel crash and host denial of service. The EPSS probability is 0.151%, reflecting a low likelihood of opportunistic exploitation in the wild.
No public proof-of-concept code has been released. The vulnerability is described in prose only because no verified exploit code is available. Refer to the upstream commits 0f5e9ddd7e8e and cb9959ab5f99 for technical details.
Detection Methods for CVE-2026-53257
Indicators of Compromise
- Unexpected kernel panics or oops messages referencing mac80211 or cfg80211 functions in dmesg or /var/log/kern.log.
- Repeated Wi-Fi interface resets or driver reloads correlated with malformed beacon or association frames.
- Crash signatures involving EHT element parsing during association, scan, or beacon processing.
Detection Strategies
- Monitor kernel logs for stack traces originating in cfg80211 or mac80211 EHT/HE element handling.
- Track running kernel versions across the fleet and flag hosts that have not received the upstream patch.
- Correlate Wi-Fi interface down events with system reboots to identify potential crash patterns.
Monitoring Recommendations
- Ingest dmesg and syslog data into a centralized logging platform with alerting on kernel oops or panic strings.
- Track kernel package versions in configuration management to confirm patch deployment.
- Audit Wi-Fi-capable Linux endpoints, including embedded and IoT devices, where stable kernel updates may lag.
How to Mitigate CVE-2026-53257
Immediate Actions Required
- Apply the upstream Linux kernel patches referenced in commits 0f5e9ddd7e8e and cb9959ab5f99 once they land in your distribution's stable kernel.
- Update affected systems to a vendor-supplied kernel build that includes the cfg80211 HE/EHT consistency enforcement.
- Restrict untrusted Wi-Fi networks and rogue access points in environments where patching cannot be performed immediately.
Patch Information
The upstream Linux kernel fix is available through two commits in the stable tree: Kernel commit 0f5e9ddd7e8e and Kernel commit cb9959ab5f99. The patches add validation in cfg80211 to require consistent HE and EHT capability and operation elements before the data reaches mac80211. Distribution maintainers are expected to backport the fix to supported long-term stable branches.
Workarounds
- Disable Wi-Fi 7 (EHT) support in driver or kernel configuration on systems that do not require it.
- Connect only to trusted, authenticated Wi-Fi networks until patches are deployed.
- For server and infrastructure hosts, disable unused wireless interfaces with rfkill block wifi or remove the driver module.
# Configuration example
# Verify running kernel and check for the cfg80211 fix
uname -r
modinfo cfg80211 | grep -i version
# Disable Wi-Fi where wireless is not required
sudo rfkill block wifi
# Optionally unload the mac80211 stack on systems that do not use Wi-Fi
sudo modprobe -r mac80211 cfg80211
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
