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CVE-2023-1998· NVD / CVE Program· CNA Google

Spectre v2 SMT mitigations problem in Linux kernel

The Linux kernel allows userspace processes to enable mitigations by calling prctl with PR_SET_SPECULATION_CTRL which disables the speculation feature as well as by using seccomp. We had noticed that on VMs of at least one major cloud provider, the kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. The same behavior can be observed on a bare-metal machine when forcing the mitigation to IBRS on boot command line. This happened because when plain IBRS was enabled (not enhanced IBRS), the kernel had some logic that determined that STIBP was not needed. The IBRS bit implicitly protects against cross-thread branch target injection. However, with legacy IBRS, the IBRS bit was cleared on returning to userspace, due to performance reasons, which disabled the implicit STIBP and left userspace threads vulnerable to cross-thread branch target injection against which STIBP protects.

MediumCVSS 5.6 · v3.1—Proof of concept Fix available
Published
Apr 21, 2023
Updated
Jun 17, 2026
EPSS
1.4% · 71th percentile
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JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.6 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.6
CNA · Google
5.6
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
linuxlinux kernel
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • linux linux kernelbefore 6.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Google). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux Kernel

    • before 6.3affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:9bpftoolbefore 7.0.0-284.25.1.el9_27.0.0-284.25.1.el9_2
AlmaLinux:9kernelbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64kbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-corebefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debugbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debug-corebefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debug-develbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debug-devel-matchedbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debug-modulesbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debug-modules-corebefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-debug-modules-extrabefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-develbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-devel-matchedbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-modulesbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-modules-corebefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-64k-modules-extrabefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-abi-stablelistsbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-corebefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-cross-headersbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-debugbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-debug-corebefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-debug-develbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-debug-devel-matchedbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2
AlmaLinux:9kernel-debug-modulesbefore 5.14.0-284.25.1.el9_25.14.0-284.25.1.el9_2

+96

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:bpftool7.0.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-284.25.1.el9_2 · AlmaLinux:9Package registry (OSV)
debian:linux6.1.20-1 · Debian:12Package registry (OSV)
opensuse:dtb-aarch645.14.21-150400.24.63.1 · openSUSE:Leap 15.4Package registry (OSV)
opensuse:kernel-default5.14.21-150400.24.63.1 · openSUSE:Leap Micro 5.3Package registry (OSV)
opensuse:kernel-default-base5.14.21-150400.24.63.1.150400.24.27.1 · openSUSE:Leap Micro 5.3Package registry (OSV)
red hat:bpftool-debuginfo0:7.0.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel-matched0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debuginfo0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel-matched0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-debuginfo0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel-matched0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debuginfo0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debuginfo-common-aarch640:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
rocky linux:kernel-rt0:5.14.0-284.25.1.rt14.310.el9_2 · Rocky Linux:9Package registry (OSV)
suse:kernel-64kb5.14.21-150400.24.63.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP4Package registry (OSV)

+8

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Exploit-DB entry ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Exploit-DB entrylocal2023-04-20

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. First PoC-1 d
  2. Published
  3. TodaySep 30, 2026+1258 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality impact
High
Integrity impact
None
Availability impact
None

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

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References

All records