Linux Kernel: security vulnerability (CVE-2026-99243)
Published Last modified Sources: BSI, Msrc Update Guide, CVE.org
What is affected, what to do
In the Linux kernel, the following vulnerability has been resolved: io-wq: order the exit bit against worker creation task work io_wq_exit_workers() cancels task work for queued worker creation with task_work_cancel_match(). That has a plain load of task->task_works. io_queue_worker_create() adds the new entry and tests IO_WQ_BIT_EXIT to cancel it if the workqueue is already on its way out.
Update Linux Kernel to version 5.15.224, Linux Kernel to version 6.1.191, Linux Kernel to version 6.6.161.
- Affected
- Linux Kernel
lt 5.15.11..5.15.224 - Linux Kernel
lt 5.16..6.1.191 - Linux Kernel
lt 6.2..6.6.161 - Linux Kernel
lt 6.7..6.12.115 - Linux Kernel
lt 6.13..6.18.60 - Linux Kernel
lt 6.19..7.2.14 - Linux Kernel
lt 7.3..7.3.1 - Linux Kernel
lt 7.4..7.4-rc1
- Linux Kernel
- Fixed in
- Linux Kernel
5.15.224 - Linux Kernel
6.1.191 - Linux Kernel
6.6.161 - Linux Kernel
6.12.115 - Linux Kernel
6.18.60 - Linux Kernel
7.2.14 - Linux Kernel
7.3.1 - Linux Kernel
7.4-rc1
- Linux Kernel
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Metrics
4.7
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
4.7
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: BSI, Msrc Update Guide, CVE.org
0.2 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 10.2
Show all metrics
- Severity
- Medium
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 54.33 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 4.7 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 4.7
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.2 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 10.2
- Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
In the Linux kernel, the following vulnerability has been resolved: io-wq: order the exit bit against worker creation task work io_wq_exit_workers() cancels task work for queued worker creation with task_work_cancel_match(). That has a plain load of task->task_works. io_queue_worker_create() adds the new entry and tests IO_WQ_BIT_EXIT to cancel it if the workqueue is already on its way out. That must be ordered. task_work_add() has a full barrier via cmpxchg(). But io_wq_exit_start() sets the bit with set_bit() which doesn't have any memory ordering. So afaict, on weakly ordered architectures the exiting task may load task_works before the store of the bit is visible. The other side tests the bit before the store is visible as well. So the entry remains queued with worker_refs and the exiting task waits on worker_done indefinitely. If the task still has rings then io_uring_del_tctx_node() provides the barrier via test_and_set_bit() in io_wq_set_exit_on_idle(). When it has closed all rings though that barrier is gone. Add the barrier after the set_bit().
Source: BSI WID Portal, BSI CSAF, Microsoft Security Update Guide, cvelistv5, NVD (NIST)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Linux | Linux |
|
|
Vendors and products
References & sources
- git.kernel.orgstable/c/0d81cdd433b0a96c5275c01b8172e0b1f71dd595
- git.kernel.orgstable/c/1432d881d99584105122760133caeff1dce7a9f7
- git.kernel.orgstable/c/31fc780b75b278d37700373d54a99fdb4117fdd6
- git.kernel.orgstable/c/67da3eec264aeb67835886720243ae2dc1463315
- git.kernel.orgstable/c/6cf012a4d5e461c788ecc9dbed67adc31a142644
- git.kernel.orgstable/c/75395db7a9b40a2e826c838e648fef8ed1a2d174
- git.kernel.orgstable/c/a63c752157eacf49f628359822666b32503d194a
- git.kernel.orgstable/c/0e5663856b69219ef2f02e04bac9f5c5be19718a
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
RejectedLinux
Record modifiedLinux
Description added or changed
Show 10 original changes
Individual changes of this event as published by NVD Type Action Before After Description changed In the Linux kernel, the following vulnerability has been resolved: io-wq: order the exit bit against worker creation task work io_wq_exit_workers() cancels task work for queued worker creation with task_work_cancel_match(). That has a plain load of task->task_works. io_queue_worker_create() adds the new entry and tests IO_WQ_BIT_EXIT to cancel it if the workqueue is already on its way out. That must be ordered. task_work_add() has a full barrier via cmpxchg(). But io_wq_exit_start() sets the bit with set_bit() which doesn't have any memory ordering. So afaict, on weakly ordered architectures the exiting task may load task_works before the store of the bit is visible. The other side tests the bit before the store is visible as well. So the entry remains queued with worker_refs and the exiting task waits on worker_done indefinitely. If the task still has rings then io_uring_del_tctx_node() provides the barrier via test_and_set_bit() in io_wq_set_exit_on_idle(). When it has closed all rings though that barrier is gone. Add the barrier after the set_bit().Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.Affected versions (publisher) added —Affected value removed. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99243.json">CVE-2026-99243</a>Reference removed kernel.org: https://git.kernel.org/stable/c/0d81cdd433b0a96c5275c01b8172e0b1f71dd595—Reference removed kernel.org: https://git.kernel.org/stable/c/0e5663856b69219ef2f02e04bac9f5c5be19718a—Reference removed kernel.org: https://git.kernel.org/stable/c/1432d881d99584105122760133caeff1dce7a9f7—Reference removed kernel.org: https://git.kernel.org/stable/c/31fc780b75b278d37700373d54a99fdb4117fdd6—Reference removed kernel.org: https://git.kernel.org/stable/c/67da3eec264aeb67835886720243ae2dc1463315—Reference removed kernel.org: https://git.kernel.org/stable/c/6cf012a4d5e461c788ecc9dbed67adc31a142644—Reference removed kernel.org: https://git.kernel.org/stable/c/75395db7a9b40a2e826c838e648fef8ed1a2d174—Reference removed kernel.org: https://git.kernel.org/stable/c/a63c752157eacf49f628359822666b32503d194a—Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Record modifiedLinux
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99243.json">CVE-2026-99243</a>Reference added —https://git.kernel.org/stable/c/0e5663856b69219ef2f02e04bac9f5c5be19718aSource identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
ReceivedLinux
Description added or changed
New references:- https://git.kernel.org/stable/c/0d81cdd433b0a96c5275c01b8172e0b1f71dd595
- https://git.kernel.org/stable/c/1432d881d99584105122760133caeff1dce7a9f7
- https://git.kernel.org/stable/c/31fc780b75b278d37700373d54a99fdb4117fdd6
- https://git.kernel.org/stable/c/67da3eec264aeb67835886720243ae2dc1463315
and 3 more references
Show 9 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —In the Linux kernel, the following vulnerability has been resolved: io-wq: order the exit bit against worker creation task work io_wq_exit_workers() cancels task work for queued worker creation with task_work_cancel_match(). That has a plain load of task->task_works. io_queue_worker_create() adds the new entry and tests IO_WQ_BIT_EXIT to cancel it if the workqueue is already on its way out. That must be ordered. task_work_add() has a full barrier via cmpxchg(). But io_wq_exit_start() sets the bit with set_bit() which doesn't have any memory ordering. So afaict, on weakly ordered architectures the exiting task may load task_works before the store of the bit is visible. The other side tests the bit before the store is visible as well. So the entry remains queued with worker_refs and the exiting task waits on worker_done indefinitely. If the task still has rings then io_uring_del_tctx_node() provides the barrier via test_and_set_bit() in io_wq_set_exit_on_idle(). When it has closed all rings though that barrier is gone. Add the barrier after the set_bit().Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99243.json">CVE-2026-99243</a>Reference added —https://git.kernel.org/stable/c/0d81cdd433b0a96c5275c01b8172e0b1f71dd595Reference added —https://git.kernel.org/stable/c/1432d881d99584105122760133caeff1dce7a9f7Reference added —https://git.kernel.org/stable/c/31fc780b75b278d37700373d54a99fdb4117fdd6Reference added —https://git.kernel.org/stable/c/67da3eec264aeb67835886720243ae2dc1463315Reference added —https://git.kernel.org/stable/c/6cf012a4d5e461c788ecc9dbed67adc31a142644Reference added —https://git.kernel.org/stable/c/75395db7a9b40a2e826c838e648fef8ed1a2d174Reference added —https://git.kernel.org/stable/c/a63c752157eacf49f628359822666b32503d194aSource identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-99243"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-99243.svg?lang=en" alt="CVE-2026-99243 – NEOSEC Intel" height="20"></a>