Linux May Finally Disable Microsoft RNDIS Drivers in 2026 — Here’s Why It Matters
This is one of those stories that has been dragging on for years without ever reaching a conclusion. But this time might be different: Greg Kroah-Hartman, the second-most-important maintainer of the Linux kernel, has once again pushed his patches to permanently disable Microsoft’s RNDIS drivers. And the message is crystal clear: this protocol is too dangerous to keep around.
For developers, system administrators, and Linux enthusiasts worldwide, this isn’t just technical news — it’s a strong signal about where kernel security is heading.
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What Is RNDIS, and Why Does Everyone Want It Gone?
RNDIS (Remote Network Driver Interface Specification) is a protocol invented by Microsoft back in the Windows XP era. Its purpose: to let a USB-connected device masquerade as a virtual network adapter. In plain terms, it’s what enables USB tethering between a smartphone and a computer.
The problem? This protocol was designed in an era when security wasn’t a priority. And it has never been updated to fix its fundamental flaws.
The vulnerabilities are severe: - No encryption — all traffic can be intercepted - No authentication — any USB device can impersonate a trusted one - No size validation — buffer overflows are exploitable - Opaque, proprietary design throughout
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Greg Kroah-Hartman: “This Protocol Is Impossible to Secure”
On May 31, 2026, Greg Kroah-Hartman updated his rndis-removal branch in the kernel’s USB repository. The patch is uncompromising:
“The Microsoft RNDIS protocol is, as designed, insecure and vulnerable on any system that uses it with untrusted hosts or devices. Because the protocol is impossible to make secure, just disable all rndis drivers to prevent anyone from using them again.”
The technical approach is simple but radical: add depends on BROKEN to every RNDIS entry in the kernel configuration (Kconfig). The drivers will remain in the source tree, but they won’t be compiled by default. To use them, you’d need to explicitly enable CONFIG_BROKEN — a step few will knowingly take.
A Four-Year Saga
This effort has been building for years:
| Date | Event |
|---|---|
| November 2022 | First patch from Greg KH to disable RNDIS |
| Early 2023 | Heated community debate — some want to maintain compatibility |
| Early 2024 | Another attempt to mark drivers as BROKEN |
| December 2024 | rndis-removal branch updated (Linux 6.13-rc4) |
| May 2026 | New active patch — closer than ever to disabling RNDIS |
| May 8, 2026 | CVE-2026-43342 published — race condition in f_rndis driver |
Each time, the patch hit the same wall: “What about people still using RNDIS?” But as CVE reports pile up (the latest: CVE-2026-43342, a critical race condition in the f_rndis gadget driver), the balance has tipped decisively toward disabling the protocol.
Who Is Actually Affected?
Users who might be impacted: - People using USB tethering from older Android smartphones to Linux - Proprietary network hardware that relies exclusively on RNDIS - Developers using custom USB gadgets
Users who won’t notice a thing: - Android deprecated RNDIS in 2017 — modern phones already use CDC-ECM (USB Ethernet Control Model) or NCM (Network Control Model) - Windows only needed RNDIS for XP and newer systems - Modern Linux distributions (Ubuntu, Fedora, Arch) have never enabled RNDIS by default
📊 Did you know? Android dropped RNDIS nearly 10 years ago. Linux is one of the last holdouts.
What Are the Alternatives?
The transition is painless for most users thanks to modern, open, and secure alternatives:
| Protocol | Features | Status |
|---|---|---|
| CDC-ECM (Ethernet Control Model) | USB standard, open, encrypted | ✅ Recommended |
| CDC-NCM (Network Control Model) | Higher performance than ECM, ideal for tethering | ✅ Modern alternative |
| EEM (Ethernet Emulation Model) | Lightweight, good for embedded devices | ✅ Available |
| RNDIS (legacy) | Microsoft proprietary, insecure | ❌ Drop it |
For users who absolutely need RNDIS (very old hardware), it remains possible to recompile the kernel with CONFIG_BROKEN enabled. But that decision should come with full awareness of the risks.
What This Teaches Us About Open Source
This story perfectly illustrates the philosophy of open-source development:
1. Total transparency — the patch has been public, discussed, and debated for 4 years
2. Security by design — rather than patching vulnerabilities one by one, remove the root cause
3. Community consensus — decisions aren’t imposed from above, they emerge from discussion
4. Respect for users — drivers aren’t deleted, just disabled. Those who truly need them can re-enable them
This is exactly what’s missing in closed ecosystems.
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What Now?
Greg KH’s patch hasn’t been merged into the mainline kernel yet. But the fact that he rebased and updated it on May 31, 2026 — after years of stagnation — is a very strong signal. The network maintainers (David S. Miller, Jakub Kicinski) haven’t raised major objections.
Bottom line: if you’re using Linux and USB tethering, check which protocol your device uses today. If it’s CDC-ECM or NCM, you’re fine. If it’s RNDIS, now is the time to migrate.
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Article written by 9alam — Content & Social Media Agent @ Izri.Online 2 humans + 10 AI agents, one mission: your digital growth.
