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FedoraOperating system · Fedoraproject

CVE-2022-42331

MEDIUM · 5.5 CVSS v3.1 Published 2023-03-21
Fix available
A fix is available. Upgrade to after 4.17.0 or later.
See remediation →
57/100
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
x86: speculative vulnerability in 32bit SYSCALL path Due to an oversight in the very original Spectre/Meltdown security work (XSA-254), one entrypath performs its speculation-safety actions too late. In some configurations, there is an unprotected RET instruction which can be attacked with a variety of speculative attacks.

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

A speculative execution vulnerability exists in Xen hypervisor's x86 32-bit SYSCALL path where speculation-safety mitigations (originally addressed in XSA-254) are performed too late. This leaves an unprotected RET instruction that can be exploited via Spectre-style speculative attacks.

MitigationApply Xen security patches for XSA-315 (CVE-2022-42331) which add proper speculation barriers earlier in the 32-bit SYSCALL entry path to protect the RET instruction.

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
FedoraOperating system
Affected:= 37= 38
XenOperating system
Affected:>= 4.5.0, <= 4.17.0

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
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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. Confirm Xen hypervisor is running
    Run 'xl list' or 'xm list' to list domains, or check for xen kernel with 'uname -a' looking for 'xen' in the kernel name
    Affected if Command fails or xen is not present - not a Xen environment
  2. Check Xen hypervisor version
    Run 'xl version' or check the xen-runtime package version with 'rpm -q xen' or 'dpkg -l xen' depending on distribution
    Affected if Version is between 4.5.0 and 4.17.0 inclusive (e.g., 4.11.0, 4.16.0)
  3. Determine if 32-bit x86 support is enabled
    Check if the host runs 32-bit Xen (check xen.gz or xen kernel config) or if 32-bit guest support is available. On the host, run 'xl info' and look for 'arch' or check if 'ia32' mode is listed. For guests, check if any 32-bit guests exist with 'xl list -l' and search for 'os_arch' or 'arch' set to 'i686' or 'i386'
    Affected if 32-bit guest support is present or the hypervisor itself runs 32-bit x86 (i686/ia32)
  4. Verify if speculation barrier patches are present
    Check hypervisor build for XSA-315 fixes by examining the SYSCALL entry path in the xen-syms binary or checking if the file /usr/lib/debug/usr/lib/debug/xen-syms* contains the improved speculation barriers near the syscall_entry point. Alternatively, review vendor security advisories for your specific Xen version to confirm XSA-315 is addressed
    Affected if The hypervisor build lacks the XSA-315 fixes and runs affected version with 32-bit guest support enabled

You are affected if you run Xen 4.5.0-4.17.0 with 32-bit guest support (i686/i386) or 32-bit hypervisor and the XSA-315 patches are not applied.

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 a release after 4.17.0
Interim mitigation

Apply Xen security patches for XSA-315 (CVE-2022-42331) which add proper speculation barriers earlier in the 32-bit SYSCALL entry path to protect the RET instruction.

Recommended fix Moderate confidence

Xen >= 4.18.0 (or the first stable release containing the XSA-42331 fix); Fedora updates via standard repository channels

  1. Upgrade Xen hypervisor to a version that includes the fix for XSA-42331 (check xenbits.xen.org for the specific security advisory)
  2. After upgrading Xen, restart the hypervisor domain (dom0) to apply the changes
  3. For Fedora systems running Xen, upgrade to a Fedora kernel-xen package that addresses this vulnerability via 'dnf update'
Caveat Hypervisor restart required; ensure virtual machines are properly suspended or can tolerate brief downtime

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

Fix this in Fedora 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
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.

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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-2022-42331 in production — separate from our analysis above.

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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
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