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QemuApplication

CVE-2021-20295

MEDIUM · 6.5 CVSS v3.1 Published 2022-04-01
Fix available
A fix is available. Upgrade to 4.2.0-34 or later.
See remediation →
67/100
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
It was discovered that the update for the virt:rhel module in the RHSA-2020:4676 (https://access.redhat.com/errata/RHSA-2020:4676) erratum released as part of Red Hat Enterprise Linux 8.3 failed to include the fix for the qemu-kvm component issue CVE-2020-10756, which was previously corrected in virt:rhel/qemu-kvm via erratum RHSA-2020:4059 (https://access.redhat.com/errata/RHSA-2020:4059). CVE-2021-20295 was assigned to that Red Hat specific security regression. For more details about the original security issue CVE-2020-10756, refer to bug 1835986 or the CVE page: https://access.redhat.com/security/cve/CVE-2020-10756.

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-2021-20295 is a Red Hat-specific security regression in the virt:rhel module for RHEL 8.3. The update released via erratum RHSA-2020:4676 failed to include the fix for CVE-2020-10756 (a qemu-kvm component vulnerability previously addressed in RHSA-2020:4059), reintroducing the original vulnerability.

MitigationApply the correct qemu-kvm updates containing the CVE-2020-10756 fix, either by ensuring erratum RHSA-2020:4059 is applied or by obtaining a corrected RHSA-2020:4676 erratum from Red Hat.

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
QemuApplication
Affected:< 4.2.0-34

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
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

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

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. Verify RHEL version
    Run 'cat /etc/redhat-release' or 'hostnamectl' to confirm RHEL 8.3 is installed
    Affected if The system is running RHEL 8.3 (the regression only affects this specific version)
  2. Identify qemu-kvm package version
    Run 'rpm -q qemu-kvm' to list the installed qemu-kvm package version
    Affected if The version is earlier than 4.2.0-34 (versions < 4.2.0-34 contain the regression)
  3. Confirm virt:rhel module usage
    Check if the virt:rhel module stream is enabled: 'yum module list virt' or 'rpm -qa | grep virt:rhel'
    Affected if The virt:rhel module stream is active on the system
  4. Review applied errata
    Run 'yum updateinfo list installed' or 'rpm -qa --qf "%{NAME} %{EPOCH}:%{VERSION}-%{RELEASE}\n" | grep qemu-kvm' to identify which RHSA errata were applied
    Affected if RHSA-2020:4676 appears in the update history but RHSA-2020:4059 is missing (indicating the regression)
  5. Check qemu-kvm component state
    Verify qemu-kvm is running as a KVM hypervisor: 'kvm-ok' or 'lsmod | grep kvm'
    Affected if KVM acceleration is enabled and qemu-kvm is actively running virtual machines

A system is affected if it runs RHEL 8.3 with qemu-kvm version below 4.2.0-34 and uses the virt:rhel module, where RHSA-2020:4676 was applied without the CVE-2020-10756 fix from RHSA-2020:4059.

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
Upgrade available Upgrade to 4.2.0-34 or later
Fixed in 4.2.0-34
Interim mitigation

Apply the correct qemu-kvm updates containing the CVE-2020-10756 fix, either by ensuring erratum RHSA-2020:4059 is applied or by obtaining a corrected RHSA-2020:4676 erratum from Red Hat.

Recommended fix High confidence

Qemu 4.2.0-34 or later (or apply RHSA-2020:4059 which contains the original CVE-2020-10756 fix)

  1. Identify the current qemu-kvm package version installed using: rpm -q qemu-kvm
  2. Update the qemu-kvm package to version 4.2.0-34 or later using the package manager: yum update qemu-kvm or dnf update qemu-kvm
  3. After the update, verify the installed version matches or exceeds 4.2.0-34 using: rpm -q qemu-kvm
  4. Reboot any running virtual machines or restart the libvirtd service if required to ensure the patched version is loaded
Caveat Standard qemu-kvm upgrade may require VM downtime; test in non-production environment first

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

Fix this in Qemu Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

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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-2021-20295 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data