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CVE-2020-26088 is a local vulnerability affecting the Linux kernel NFC subsystem.
The flaw resides specifically within the socket creation handler in net/nfc/rawsock.c.
When userspace applications create raw NFC sockets, validation checks are required.
The kernel must verify if the calling process holds the CAP_NET_RAW capability.
This capability check restricts unprivileged users from crafting low-level network frames.
Due to a missing validation check during initialization, this check was omitted.
Consequently, local unprivileged attackers can create raw NFC sockets without permissions.
This authorization bypass breaks the security model of socket creation routines.
An attacker can open raw sockets to interact directly with NFC communication layers.
The vulnerability allows unauthorized manipulation of low-level protocol control data.
Upstream developers addressed this issue by introducing the missing capability verification.
The patch checks sock_net(sk)->user_ns and capable(CAP_NET_RAW) during creation.
Linux kernel version 5.8.2 includes the official fix for this security flaw.
Vendors maintaining LTS kernels must backport this commit to protect downstream users.
Automated tools like CVEhound help detect missing fixes in vendor kernel archives.
DailyCVE Form:
Platform: Linux Kernel NFC
Version: Below 5.8.2 kernels
Vulnerability : Missing capability check
Severity: Medium risk level
date: September 24 2020
Prediction: Already officially patched
What Undercode Say:
To scan kernel source code for missing fixes using CVEhound:
$python3 -m pip install –user ‘cvehound[bash]’$ cvehound –kernel ~/linux-source –files net/nfc/rawsock.c
To inspect the upstream commit containing the security fix:
$ git show 26896f01467a28651f7a536143fe5ac8449d4041
Exploit: (Educational Purposes!)
An unprivileged user executes a program invoking the socket system call.
Parameters passed include AF_NFC and SOCK_RAW to establish communication.
The kernel fails to validate CAP_NET_RAW during the socket allocation routine.
The system successfully returns a file descriptor for the raw socket.
The attacker can now inject and capture custom NFC frames directly.
Protection: from this CVE
Upgrade the Linux kernel to version 5.8.2 or newer.
Apply vendor-supplied security patches to all affected LTS kernel branches.
Disable the NFC kernel module if it is not actively required:
echo “install nfc /bin/true” >> /etc/modprobe.d/disable-nfc.conf
Impact:
Local users can bypass capability restrictions when creating raw sockets.
Potential unauthorized interaction with NFC controller hardware drivers.
Increased risk of local security boundary violations and privilege misuse.
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Sources:
Reported By: github.com
Extra Source Hub:
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