From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ED103477E51 for ; Wed, 13 May 2026 15:09:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778684959; cv=none; b=lF3Ony4QuVpQC7gkMabjL/WOz7OUI9FN+lTGnGQODPfzw9p8JHsy+DxkMLD0F3Sdgi81f3w9BkQP8Nyem6e6vMSKNf3HfBKXZycuUFe8hMXj8S4LfdY3VBqKrZOd5gG5wH8knxVI7DVQLKQlXYTcNx1scM1cQao15ZCJ27X598E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778684959; c=relaxed/simple; bh=CwM+OPCo4WkuXCxmdQ04SPs9MkMrd8Eu1uF5nrLLJmE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=BFU6aCS8HBh/KoqPGtk5hV0gcnfAAx0VD0EZWrkMA9m+DTFSuWMHqWGCOQsfVCTucPMcA+mhUY/68FtYhNbE02uRT1q2nxQeucU8bNXOtpeiacinsRX/sjx0jDRX520s7u9wJB46wIY8QMiK/Ob2Kh4YVFmem54/U7UpSC+ngfE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=W0VUyfv+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="W0VUyfv+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BE3FC19425; Wed, 13 May 2026 15:09:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778684958; bh=CwM+OPCo4WkuXCxmdQ04SPs9MkMrd8Eu1uF5nrLLJmE=; h=From:To:Cc:Subject:Date:Reply-To:From; b=W0VUyfv+R4AXwCegYcIHn/bN0AwlCVVXIReUUCrxkgtb6XhRWCapgYmyF+OHwsb6n xfYLHqK+mgp8r+MkTLv+hhHryrl+PlPnOQSwpQp+jTnAYQT5+86SGjwzsFPoZdoSuX YHzF6C0tH8Hvhi604mHp9TouTbuu4fpsPsbX7Jcc= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43483: KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated Date: Wed, 13 May 2026 17:08:51 +0200 Message-ID: <2026051349-CVE-2026-43483-1337@gregkh> X-Mailer: git-send-email 2.54.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3764; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=ZLjP7xLCywkstM0rBGUz9KSNUcxzhvDGED7CMo5I3Fs=; b=owGbwMvMwCRo6H6F97bub03G02pJDFksUxivry0Pnan46dmBK8d7hWedNn//PWLq8m6WrPfZA l6v65/d7YhlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJZFxkWHD+lLzj6tPtFd1K 6dv8Te/Z7SxrZ2aY7yaypShQvFWNuyf28nqPf9t/K0gGAQA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated Explicitly set/clear CR8 write interception when AVIC is (de)activated to fix a bug where KVM leaves the interception enabled after AVIC is activated. E.g. if KVM emulates INIT=>WFS while AVIC is deactivated, CR8 will remain intercepted in perpetuity. On its own, the dangling CR8 intercept is "just" a performance issue, but combined with the TPR sync bug fixed by commit d02e48830e3f ("KVM: SVM: Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active"), the danging intercept is fatal to Windows guests as the TPR seen by hardware gets wildly out of sync with reality. Note, VMX isn't affected by the bug as TPR_THRESHOLD is explicitly ignored when Virtual Interrupt Delivery is enabled, i.e. when APICv is active in KVM's world. I.e. there's no need to trigger update_cr8_intercept(), this is firmly an SVM implementation flaw/detail. WARN if KVM gets a CR8 write #VMEXIT while AVIC is active, as KVM should never enter the guest with AVIC enabled and CR8 writes intercepted. [Squash fix to avic_deactivate_vmcb. - Paolo] The Linux kernel CVE team has assigned CVE-2026-43483 to this issue. Affected and fixed versions =========================== Issue introduced in 4.7 with commit 3bbf3565f48ce3999b5a12cde946f81bd4475312 and fixed in 6.1.167 with commit a4123fe5d9122eef9852e4921f7cc463420f30d4 Issue introduced in 4.7 with commit 3bbf3565f48ce3999b5a12cde946f81bd4475312 and fixed in 6.6.130 with commit 816fa1dfae4532e851b1fe6b2434c753ecbd86c7 Issue introduced in 4.7 with commit 3bbf3565f48ce3999b5a12cde946f81bd4475312 and fixed in 6.12.78 with commit 01651e7751edbbc0fb4598f8367a3dabcfc8c182 Issue introduced in 4.7 with commit 3bbf3565f48ce3999b5a12cde946f81bd4475312 and fixed in 6.18.19 with commit ba3bca40f9f25c053f69413e5f4a41dd0fd762bf Issue introduced in 4.7 with commit 3bbf3565f48ce3999b5a12cde946f81bd4475312 and fixed in 6.19.9 with commit 737410b32bd615b321da4fbeda490351b9af5e8b Issue introduced in 4.7 with commit 3bbf3565f48ce3999b5a12cde946f81bd4475312 and fixed in 7.0 with commit 87d0f901a9bd8ae6be57249c737f20ac0cace93d 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-2026-43483 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: arch/x86/kvm/svm/avic.c arch/x86/kvm/svm/svm.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/a4123fe5d9122eef9852e4921f7cc463420f30d4 https://git.kernel.org/stable/c/816fa1dfae4532e851b1fe6b2434c753ecbd86c7 https://git.kernel.org/stable/c/01651e7751edbbc0fb4598f8367a3dabcfc8c182 https://git.kernel.org/stable/c/ba3bca40f9f25c053f69413e5f4a41dd0fd762bf https://git.kernel.org/stable/c/737410b32bd615b321da4fbeda490351b9af5e8b https://git.kernel.org/stable/c/87d0f901a9bd8ae6be57249c737f20ac0cace93d