CVE-2026-99059: wireguard: noise: reject response consumption after intermediate initiation

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

wireguard: noise: reject response consumption after intermediate initiation

Two threads begin processing the identical response message, received
twice. The first thread, A, runs. While it's running, the second one,
B, gets partway through, and during that slow calculation, or even while
blocking on down_write(), A completes and then also a handshake
initiation that's already been queued up runs in thread C, which itself
takes that same down_write(). The handshake initiation creation
succeeds, and sets the state back to waiting-for-response, and calls
up_write(), at which point thread B resumes, because either its finished
its calculations or was finally allowed to acquire down_write(). Thread
B then copies the state back to the peer, and begins a new session,
using that state, which is the same session as the one made in thread A.

Thread A			Thread B			Thread C

down_read()
 sA = handshake->state
 memcpy(cA, handshake->crypto)
up_read()
if (sA != 1)
 goto fail
slow_crypto(cA)
				down_read()
				 sB = handshake->state
				 memcpy(cB, handshake->crypto)
				up_read()
				if (sB != 1)
				 goto fail
				slow_crypto(cB)
down_write()
 if (sA != handshake->state)
  goto fail
 memcpy(handshake->crypto, cA)
 handshake->state = 2
up_write()
down_write()
 if (handshake->state != 2)
  goto fail
 derive_session(handshake->crypto)
up_write()
								down_write()
								 slow_crypto(handshake->crypto)
								 handshake->state = 1
								up_write()
				down_write()
				 if (sB != handshake->state)
				   goto fail
				 memcpy(handshake->crypto, cB)
				 handshake->state = 2
				up_write()
				down_write()
				 if (handshake->state != 2)
				  goto fail
				 derive_session(handshake->crypto)
				up_write()

This seems basically impossible to hit in a meaningful way in practice,
but ensure that it absolutely cannot happen by comparing the ephemeral
private key that's on the stack with the latest one that the peer's
handshake state has.

The Linux kernel CVE team has assigned CVE-2026-99059 to this issue.


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

	Issue introduced in 5.6 with commit e7096c131e5161fa3b8e52a650d7719d2857adfd and fixed in 6.6.160 with commit fb5ce4c7790c3eeec820302d08d70ecf46af4295
	Issue introduced in 5.6 with commit e7096c131e5161fa3b8e52a650d7719d2857adfd and fixed in 6.12.113 with commit c76a80db593096edf2b3b3972f58b6342a8c6c04
	Issue introduced in 5.6 with commit e7096c131e5161fa3b8e52a650d7719d2857adfd and fixed in 6.18.57 with commit 4d64a3d6e96aa78619c9c29ffde309794974588a
	Issue introduced in 5.6 with commit e7096c131e5161fa3b8e52a650d7719d2857adfd and fixed in 7.2.11 with commit 3bec3d32c2a3afd164fc87f95457df2cf9049c20
	Issue introduced in 5.6 with commit e7096c131e5161fa3b8e52a650d7719d2857adfd and fixed in 7.3 with commit d0305f8d90029556260c6824b61c493c424eba9e

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-2026-99059
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/net/wireguard/noise.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/fb5ce4c7790c3eeec820302d08d70ecf46af4295
	https://git.kernel.org/stable/c/c76a80db593096edf2b3b3972f58b6342a8c6c04
	https://git.kernel.org/stable/c/4d64a3d6e96aa78619c9c29ffde309794974588a
	https://git.kernel.org/stable/c/3bec3d32c2a3afd164fc87f95457df2cf9049c20
	https://git.kernel.org/stable/c/d0305f8d90029556260c6824b61c493c424eba9e