CVE-2026-98577: nfc: llcp: fix WKS SAP hijacking via prefix match in nfc_llcp_wks_sap()

CVE-2026-98577: nfc: llcp: fix WKS SAP hijacking via prefix match in nfc_llcp_wks_sap()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

nfc: llcp: fix WKS SAP hijacking via prefix match in nfc_llcp_wks_sap()

nfc_llcp_wks_sap() compares only service_name_len bytes, so a short
service_name like "u" matches longer WKS strings like "urn:nfc:sn:snep".
Fix by requiring exact length match before strncmp().

The Linux kernel CVE team has assigned CVE-2026-98577 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 5.10.271 with commit 0c83a8a45fed256ccc5fe7160b436b671fc79fb8
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 5.15.222 with commit aa555ed5ed0d15efbaf27e0e9f152a6df715278a
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 6.1.189 with commit 32b5f0b338bf59391a1cff9a6190a72c4d2c1ba8
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 6.6.158 with commit 6fad2c34d451d11a9f3f946cae1105fee91d96b8
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 6.12.112 with commit bf41af8f910cbb5d776a1dfa0671d31a7e262e28
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 6.18.55 with commit f234197f3bda3aea5d4b1e591d6bcb3660a8b3fc
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 7.2.9 with commit 0a0412745c86acd089c6460da715ab966b1615e7
	Issue introduced in 3.3 with commit d646960f7986fefb460a2b062d5ccc8ccfeacc3a and fixed in 7.3-rc5 with commit 408cff6bd60636df201274d320edfdfde9ed41db

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-98577
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/nfc/llcp_core.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/0c83a8a45fed256ccc5fe7160b436b671fc79fb8
	https://git.kernel.org/stable/c/aa555ed5ed0d15efbaf27e0e9f152a6df715278a
	https://git.kernel.org/stable/c/32b5f0b338bf59391a1cff9a6190a72c4d2c1ba8
	https://git.kernel.org/stable/c/6fad2c34d451d11a9f3f946cae1105fee91d96b8
	https://git.kernel.org/stable/c/bf41af8f910cbb5d776a1dfa0671d31a7e262e28
	https://git.kernel.org/stable/c/f234197f3bda3aea5d4b1e591d6bcb3660a8b3fc
	https://git.kernel.org/stable/c/0a0412745c86acd089c6460da715ab966b1615e7
	https://git.kernel.org/stable/c/408cff6bd60636df201274d320edfdfde9ed41db