linux-cve-announce - CVE-2026-23194: rust_binder: correctly handle FDA objects of length zero

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Message-ID: <2026021434-CVE-2026-23194-5976@gregkh>
Date: Sat, 14 Feb 2026 17:28:51 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23194: rust_binder: correctly handle FDA objects of length zero

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

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

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

rust_binder: correctly handle FDA objects of length zero

Fix a bug where an empty FDA (fd array) object with 0 fds would cause an
out-of-bounds error. The previous implementation used `skip == 0` to
mean "this is a pointer fixup", but 0 is also the correct skip length
for an empty FDA. If the FDA is at the end of the buffer, then this
results in an attempt to write 8-bytes out of bounds. This is caught and
results in an EINVAL error being returned to userspace.

The pattern of using `skip == 0` as a special value originates from the
C-implementation of Binder. As part of fixing this bug, this pattern is
replaced with a Rust enum.

I considered the alternate option of not pushing a fixup when the length
is zero, but I think it's cleaner to just get rid of the zero-is-special
stuff.

The root cause of this bug was diagnosed by Gemini CLI on first try. I
used the following prompt:

> There appears to be a bug in @drivers/android/binder/thread.rs where
> the Fixups oob bug is triggered with 316 304 316 324. This implies
> that we somehow ended up with a fixup where buffer A has a pointer to
> buffer B, but the pointer is located at an index in buffer A that is
> out of bounds. Please investigate the code to find the bug. You may
> compare with @drivers/android/binder.c that implements this correctly.

The Linux kernel CVE team has assigned CVE-2026-23194 to this issue.

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

	Issue introduced in 6.18 with commit eafedbc7c050c44744fbdf80bdf3315e860b7513 and fixed in 6.18.10 with commit 598fe3ff32e43918ed8a062f55432b3d23e6340c
	Issue introduced in 6.18 with commit eafedbc7c050c44744fbdf80bdf3315e860b7513 and fixed in 6.19 with commit 8f589c9c3be539d6c2b393c82940c3783831082f

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-2026-23194
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:
	drivers/android/binder/thread.rs

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/598fe3ff32e43918ed8a062f55432b3d23e6340c
	https://git.kernel.org/stable/c/8f589c9c3be539d6c2b393c82940c3783831082f