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Debian LinuxOperating system · Debian

CVE-2022-23040

HIGH · 7.0 CVSS v3.1 Published 2022-03-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
72/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Linux PV device frontends vulnerable to attacks by backends T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Several Linux PV device frontends are using the grant table interfaces for removing access rights of the backends in ways being subject to race conditions, resulting in potential data leaks, data corruption by malicious backends, and denial of service triggered by malicious backends: blkfront, netfront, scsifront and the gntalloc driver are testing whether a grant reference is still in use. If this is not the case, they assume that a following removal of the granted access will always succeed, which is not true in case the backend has mapped the granted page between those two operations. As a result the backend can keep access to the memory page of the guest no matter how the page will be used after the frontend I/O has finished. The xenbus driver has a similar problem, as it doesn't check the success of removing the granted access of a shared ring buffer. blkfront: CVE-2022-23036 netfront: CVE-2022-23037 scsifront: CVE-2022-23038 gntalloc: CVE-2022-23039 xenbus: CVE-2022-23040 blkfront, netfront, scsifront, usbfront, dmabuf, xenbus, 9p, kbdfront, and pvcalls are using a functionality to delay freeing a grant reference until it is no longer in use, but the freeing of the related data page is not synchronized with dropping the granted access. As a result the backend can keep access to the memory page even after it has been freed and then re-used for a different purpose. CVE-2022-23041 netfront will fail a BUG_ON() assertion if it fails to revoke access in the rx path. This will result in a Denial of Service (DoS) situation of the guest which can be triggered by the backend. CVE-2022-23042

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

CVE-2022-23040 is a race condition vulnerability in the Xen xenbus driver within Linux PV (paravirtualization) frontends. The driver fails to check the success status when removing granted access to shared ring buffers, allowing a malicious backend to retain memory access after the frontend has attempted to revoke it. Combined with a related issue (CVE-2022-23042) affecting multiple drivers including xenbus where freeing grant reference data pages is not synchronized with dropping access, this enables data leaks, data corruption, and DoS attacks by malicious Xen backends.

MitigationApply Linux kernel updates that fix grant table reference counting and synchronization in xenbus and related PV frontend drivers. For systems not immediately patchable, consider restricting VM migration or ensuring trust in all VM backends within the same Xen host.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 9.0
XenOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if the system is a Xen paravirtualized guest
    Check for Xen hypervisor presence by running 'xl list' or 'xm list' (if tools installed), or look for 'xen' in /proc/xen/, or check dmesg for 'Xen:' messages. Alternatively, check if /proc/xen/candidates or /proc/xen/balloon exists.
    Affected if The system is running as a Linux PV (paravirtualized) guest on a Xen hypervisor and uses xenbus for communication with the backend.
  2. Check the installed Linux kernel version
    Run 'uname -r' to get the kernel version, then compare against known patched versions for your distribution. For Debian 9, patched kernels include 4.9.0-18+deb9u1 or later in the 4.9 series.
    Affected if The kernel version is older than the patched versions for your distribution and the system is a Xen PV guest.
  3. Verify if the xenbus frontend driver is in use
    Check for xenbus device presence by running 'ls -la /dev/xen/' (if it exists), or check 'lsmod | grep xen' to see if xenbus, xenfs, or other Xen frontend modules are loaded, or check /sys/hypervisor/ for Xen entries.
    Affected if The xenbus driver module is loaded and actively used for PV communication with the Xen backend.
  4. Check for active grant table references
    Inspect /proc/xen/balloon (if available) or use 'xl info' to see memory allocation details. Review any running VM configuration for grant table usage with 'xl list -l <vmname>' or check dmesg for xen grant table messages.
    Affected if The VM is using grant tables for memory sharing with the backend, which is the normal PV operation mode.
  5. Inspect Xen backend trust and configuration
    Review the VM configuration file (if you have access) for backend settings, or check the host side (if you are the host admin) for all VMs on the same host with 'xl list' to identify potentially untrusted backends.
    Affected if The VM shares a Xen host with backend VMs that may be untrusted or compromised, as the vulnerability allows a malicious backend to retain memory access.

A system is affected if it runs as a Xen PV guest with an unpatched Linux kernel and uses xenbus for paravirtualized communication, especially in multi-tenant environments with untrusted co-resident VMs.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Linux kernel updates that fix grant table reference counting and synchronization in xenbus and related PV frontend drivers. For systems not immediately patchable, consider restricting VM migration or ensuring trust in all VM backends within the same Xen host.

Recommended fix Moderate confidence

Debian 9.0: Linux kernel from Debian stretch security updates; Xen: version with CVE-2022-23040 fix applied (check xenbits.xenproject.org for specific fixed release)

  1. Check current kernel version with: uname -r
  2. Check current Xen version with: xl version or xl info | grep xen_changeset
  3. For Debian 9.0 (stretch): Update package lists with: apt-get update
  4. Apply Debian security updates for the Linux kernel: apt-get install linux-image-<version> (replace with latest available from Debian security)
  5. Reboot the system to apply the new kernel
  6. For Xen hypervisor: Apply Xen security patches from xenbits.xenproject.org or upgrade Xen to a version that includes the fix for CVE-2022-23040
  7. Verify the fix by checking that the xenbus driver no longer has the race condition - confirm successful grant removal checking is implemented in the running kernel
Caveat Kernel update may require system reboot and could affect PV driver behavior; ensure backups and test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2022-23040 in production — separate from our analysis above.

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What this is

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