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.
- BDU:2023-02115
- ALSA-2023:4377
- ALSA-2023:4378
- RHSA-2023:4377
- RHSA-2023:4378
- RHSA-2023:5603
- RHSA-2023:5604
- RHSA-2024:3810
- RLSA-2023:4378
- SUSE-SU-2023:2140-1
- SUSE-SU-2023:2141-1
- SUSE-SU-2023:2146-1
- SUSE-SU-2023:2147-1
- SUSE-SU-2023:2148-1
- SUSE-SU-2023:2151-1
- SUSE-SU-2023:2156-1
- SUSE-SU-2023:2162-1
- SUSE-SU-2023:2163-1
- SUSE-SU-2023:2231-1
- SUSE-SU-2023:2232-1
- Published
- Apr 21, 2023
- Updated
- Jun 17, 2026
- EPSS
- 1.4% · 71th percentile
- CWE
- CWE-1303
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Report tools
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
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
| debian | debian linux | cpe:2.3:o:debian:debian_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.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:9 | bpftool | before 7.0.0-284.25.1.el9_2 | 7.0.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-core | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug-core | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug-devel | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug-devel-matched | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug-modules | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug-modules-core | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-debug-modules-extra | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-devel | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-devel-matched | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-modules | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-modules-core | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-64k-modules-extra | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-abi-stablelists | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-core | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-cross-headers | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-debug | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-debug-core | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-debug-devel | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-debug-devel-matched | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
| AlmaLinux:9 | kernel-debug-modules | before 5.14.0-284.25.1.el9_2 | 5.14.0-284.25.1.el9_2 |
+96
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
- CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV83Now
- CVE-2019-13272In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to creKEV77This week
- CVE-2013-6282The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the v6k and v7 ARM platforms do not validate certain addKEV77This week
- CVE-2013-2094The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9 uses an incorrect integer data type, which allows loKEV77This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:bpftool | 7.0.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-core | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-core | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-devel | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-devel-matched | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules-core | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules-extra | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-devel | 5.14.0-284.25.1.el9_2 · AlmaLinux:9 | Package registry (OSV) |
| debian:linux | 6.1.20-1 · Debian:12 | Package registry (OSV) |
| opensuse:dtb-aarch64 | 5.14.21-150400.24.63.1 · openSUSE:Leap 15.4 | Package registry (OSV) |
| opensuse:kernel-default | 5.14.21-150400.24.63.1 · openSUSE:Leap Micro 5.3 | Package registry (OSV) |
| opensuse:kernel-default-base | 5.14.21-150400.24.63.1.150400.24.27.1 · openSUSE:Leap Micro 5.3 | Package registry (OSV) |
| red hat:bpftool-debuginfo | 0:7.0.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-debuginfo | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-devel | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-devel-matched | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debuginfo | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-devel | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-devel-matched | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debug-debuginfo | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debug-devel | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debug-devel-matched | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debuginfo | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debuginfo-common-aarch64 | 0:5.14.0-284.25.1.el9_2 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| rocky linux:kernel-rt | 0:5.14.0-284.25.1.rt14.310.el9_2 · Rocky Linux:9 | Package registry (OSV) |
| suse:kernel-64kb | 5.14.21-150400.24.63.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP4 | Package 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.
| Source | Kind | Date |
|---|---|---|
| Exploit-DB entry | local | 2023-04-20 |
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.
- First PoC-1 d
- Published
- TodaySep 30, 2026+1258 d
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.
Credits
All researchersFinders, 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
Weakness class (CWE)
CWE-1303 · Non-Transparent Sharing of Microarchitectural ResourcesCVSS 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.
Attack patterns (CAPEC)
ATT&CK techniques
—
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 helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/torvalds/linux/commit/6921ed9049bc7457f66c1596c5b78aec0dae4a9d
- kernel.dance/#6921ed9049bc7457f66c1596c5b78aec0dae4a9d
- lists.debian.org/debian-lts-announce/2023/05/msg00005.html
- lists.debian.org/debian-lts-announce/2023/05/msg00006.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.