linux-cve-announce - CVE-2025-39926: genetlink: fix genl

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Message-ID: <2025100125-CVE-2025-39926-06ea@gregkh>
Date: Wed,  1 Oct 2025 10:07:26 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39926: genetlink: fix genl_bind() invoking bind() after -EPERM

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

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

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

genetlink: fix genl_bind() invoking bind() after -EPERM

Per family bind/unbind callbacks were introduced to allow families
to track multicast group consumer presence, e.g. to start or stop
producing events depending on listeners.

However, in genl_bind() the bind() callback was invoked even if
capability checks failed and ret was set to -EPERM. This means that
callbacks could run on behalf of unauthorized callers while the
syscall still returned failure to user space.

Fix this by only invoking bind() after "if (ret) break;" check
i.e. after permission checks have succeeded.

The Linux kernel CVE team has assigned CVE-2025-39926 to this issue.


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

	Issue introduced in 6.9 with commit 3de21a8990d3c2cc507e9cc4ed00f36358d5b93e and fixed in 6.12.48 with commit 98c9d884047a3051c203708914a874dece3cbe54
	Issue introduced in 6.9 with commit 3de21a8990d3c2cc507e9cc4ed00f36358d5b93e and fixed in 6.16.8 with commit 8858c1e9405906c09589d7c336f04058ea198207
	Issue introduced in 6.9 with commit 3de21a8990d3c2cc507e9cc4ed00f36358d5b93e and fixed in 6.17 with commit 1dbfb0363224f6da56f6655d596dc5097308d6f5

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-2025-39926
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/netlink/genetlink.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/98c9d884047a3051c203708914a874dece3cbe54
	https://git.kernel.org/stable/c/8858c1e9405906c09589d7c336f04058ea198207
	https://git.kernel.org/stable/c/1dbfb0363224f6da56f6655d596dc5097308d6f5