CVE-2026-74564: netfilter: xt_hashlimit: validate hashtable supports XT_HASHLIMIT_RATE_MATCH

From: Greg Kroah-Hartman <[email protected]>

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

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

netfilter: xt_hashlimit: validate hashtable supports XT_HASHLIMIT_RATE_MATCH

The XT_HASHLIMIT_RATE_MATCH flag mode changes the semantics of the
dsthash_ent structure which represents an entry in the hashtable.  There
is a union area which uses a different layout to express the rate match
mode.

Update .checkentry path to validate the XT_HASHLIMIT_RATE_MATCH mode
flag is requested by two or more different rules that refer to the same
hashtable. Otherwise, uninitialized access to the burst field in the
union is possible.

Reject the use of the XT_HASHLIMIT_RATE_MATCH mode flag if set on by
revision less than 3 too.

The Linux kernel CVE team has assigned CVE-2026-74564 to this issue.


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

	Issue introduced in 4.14 with commit bea74641e3786d51dcf1175527cc1781420961c9 and fixed in 6.6.151 with commit 24683fea1f06bd3bd2707b99460e859bc6464c22
	Issue introduced in 4.14 with commit bea74641e3786d51dcf1175527cc1781420961c9 and fixed in 6.12.103 with commit 32ec8d4aba2cf22e12bdc28df8c4bd833c195fc0
	Issue introduced in 4.14 with commit bea74641e3786d51dcf1175527cc1781420961c9 and fixed in 6.18.44 with commit d186f77d18bdfb252d401ff992ca3001a6a65a0f
	Issue introduced in 4.14 with commit bea74641e3786d51dcf1175527cc1781420961c9 and fixed in 7.1.8 with commit 06a76334243ccd875a981aa8bb46c0f931ef1e3b
	Issue introduced in 4.14 with commit bea74641e3786d51dcf1175527cc1781420961c9 and fixed in 7.2-rc6 with commit 305b63e1402267459fdabb183af4527f6799eebf

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-2026-74564
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/netfilter/xt_hashlimit.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/24683fea1f06bd3bd2707b99460e859bc6464c22
	https://git.kernel.org/stable/c/32ec8d4aba2cf22e12bdc28df8c4bd833c195fc0
	https://git.kernel.org/stable/c/d186f77d18bdfb252d401ff992ca3001a6a65a0f
	https://git.kernel.org/stable/c/06a76334243ccd875a981aa8bb46c0f931ef1e3b
	https://git.kernel.org/stable/c/305b63e1402267459fdabb183af4527f6799eebf