HighCVE-2026-98981

Linux Kernel: security vulnerability (CVE-2026-98981)

Published 23.10.2026Last modified 30.10.2026Sources: CVE.org, Msrc Update Guide, BSI

What is affected, what to do

Update Linux Kernel to version 5.10.273, Linux Kernel to version 5.15.224, Linux Kernel to version 6.1.191.

Affected: Linux Kernel lt 3.18..5.10.273
Linux Kernel lt 5.11..5.15.224
Linux Kernel lt 5.16..6.1.191
Linux Kernel lt 6.2..6.6.160
Linux Kernel lt 6.7..6.12.114
Linux Kernel lt 6.13..6.18.57
Linux Kernel lt 6.19..7.2.11
Fixed in: Linux Kernel 5.10.273
Linux Kernel 5.15.224
Linux Kernel 6.1.191
Linux Kernel 6.6.160
Linux Kernel 6.12.114
Linux Kernel 6.18.57
Linux Kernel 7.2.11
Linux Kernel 7.3

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Metrics

8.8

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

8.8

CVSS v3

Severity High on the scale from 0 to 10.

Source: CVE.org, Msrc Update Guide, BSI

0.2 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 5.5

Show all metrics

Severity: High
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: 74.24 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: 8.8 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: 8.8
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: 5.5; Low — this CVE sits in the lower 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: 23.10.2026

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: High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
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:

namespace: unhash a dentry before detaching the mounts on it

unlink(), rmdir() and rename() remove the entry from the filesystem, call detach_mounts() on the entry with the inode locked and then call d_delete() once the inode is unlocked.

The thing is that between detach_mounts() and d_delete() the dentry is still hashed and positive. But after detach_mounts() nothing covers the dentry anymore. A lookup that finds this dentry in the dcache can uncover what the mounts hid.

That's a problem when unlinking files or directories that are mountpoints in other mount namespaces. Everybody who had the underlying entry covered can race the detach_mount() call until d_delete() has run.

The race window isn't all that small. It encompasses namespace_unlock() with a full synchronize_rcu_expedited() grace period and the inode_unlock() of the entry.

In my experiments three walkers that kept trying read an overmounted file in 11938 of the 16140 unlinks that removed its mountpoint from a bind mount of the filesystem within a minute.

Fun fact, d_invalidate() has the same ordering problem but gets it right. It unhashes the dentry first and detaches the mounts afterwards. Let's do the same in __detach_mounts():

A lookup that hasn't found the dentry yet misses it in the dcache and waits for the directory lock that the caller holds until the name is gone for good.
A lockless lookup that found it already fails the mount_lock check while the dentry still counts as a mountpoint and the d_seq check once it doesn't, and retries.

This fixes the lockless path. We still need to fix the reference count lookup in a follow-up patch.

So d_drop() the dentry. The dentry stays positive and held but can't be found anymore. Then proceed with the detach and unlink.

Reproducer:

The reads were counted with the program below, three walkers for 60 s in a VM with 4 CPUs. The race window is stretched with the debug patch pasted here. fs.detach_race_walk_us sleeps in lookup_fast() once it found a mountpoint dentry and before its mounts are crossed. fs.detach_race_unlink_us sleeps in vfs_unlink() between detach_mounts() and d_delete().

// SPDX-License-Identifier: GPL-2.0 /*

unlink_covered: unlink a file that is a mountpoint in a detached copy of
its mount, against lookups that open it through that copy.
A is a tmpfs with the file f1 (content SECRET_F) and the plain file
MARK_A. A' is an open_tree(OPEN_TREE_CLONE) copy of A with MARK_A bound
on A'/f1, held through an O_PATH fd on its root once the tree fd is
closed. Walkers open f1 through that fd while the driver unlinks A/f1,
where nothing is mounted on it. A walker may read MARK_A or get ENOENT.
A read of SECRET_F is a hit: the name was found after its mount was
gone. The lockless walks use openat2(RESOLVE_CACHED).
usage: unlink_covered [-t seconds] [-w walkers] */ #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif #include <errno.h> #include <fcntl.h> #include <pthread.h> #include <stdatomic.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/mount.h> #include <sys/stat.h> #include <sys/syscall.h> #include <linux/openat2.h>

#ifndef __NR_open_tree #define __NR_open_tree 428 #endif #ifndef __NR_move_mount #define __NR_move_mount 429 #endif #ifndef __NR_openat2 #define __NR_openat2 437 #endif #ifndef OPEN_TREE_CLONE #define OPEN_TREE_CLONE 1 #endif #ifndef OPEN_TREE_CLOEXEC #define OPEN_TREE_CLOEXEC O_CLOEXEC #endif #ifndef MOVE_MOUNT_F_EMPTY_PATH #define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 #endif

#define WORK "/tmp/uc" #define ADIR WORK "/A"

static int duration = 60, nwalkers = 3; static atomic_int stop, writer_waiting; static pthread_rwlock_t cur_lock = PTHREAD_RWLOCK_INITIALIZER; static int cur_fd = -1; /* the root of A', -1 wh ---truncated---

Source: cvelistv5, NVD (NIST), Microsoft Security Update Guide, BSI CSAF, BSI WID Portal

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Linux	Linux	`6.7 – < 6.12.114` `6.19 – < 7.2.11` `5.11 – < 5.15.224` `5.16 – < 6.1.191` `—` `6.13 – < 6.18.57` `3.18 – < 5.10.273` `6.2 – < 6.6.160`	`6.12.114` `7.2.11` `5.15.224` `6.1.191` `7.3` `6.18.57` `5.10.273` `6.6.160`

Vendors and products

Linux Linux

References & sources

git.kernel.orgstable/c/528b383dc35d1e5caf64ddf5d35f983ae543b0d0
git.kernel.orgstable/c/8300de4aa5d09061bfcf2af5b52c0cdba3873185
git.kernel.orgstable/c/8d71bfc9b3fc15d7103e82ea9dc5057541866e46
git.kernel.orgstable/c/d29cd99db3db74cf3447be74d25740981789d461
git.kernel.orgstable/c/db90eecbde319527aa9480c039d32a0f5fe80574
git.kernel.orgstable/c/97cc290c57ea04337fd33912d780367add41525c
git.kernel.orgstable/c/b3fa3811ffffa130586c4ff8f7299b7fc69216d5
git.kernel.orgstable/c/bb917ec497f6099c6cb9375596e085a5f6b52ff2

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).

30.10.2026Record modifiedLinux

New references:

Show 4 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/2026/98xxx/CVE-2026-98981.json">CVE-2026-98981</a>
Reference	added	—	https://git.kernel.org/stable/c/97cc290c57ea04337fd33912d780367add41525c
Reference	added	—	https://git.kernel.org/stable/c/b3fa3811ffffa130586c4ff8f7299b7fc69216d5
Reference	added	—	https://git.kernel.org/stable/c/bb917ec497f6099c6cb9375596e085a5f6b52ff2

Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

24.10.2026Record modifiedLinux
CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Show the original change
Individual changes of this event as published by NVD
Type Action Before After
CVSS added
—
AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Individual changes of this event as published by NVD
Type	Action	Before	After
CVSS	added	—	AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

23.10.2026ReceivedLinux

Description added or changed

New references:

and 1 more reference

Show 7 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: namespace: unhash a dentry before detaching the mounts on it unlink(), rmdir() and rename() remove the entry from the filesystem, call detach_mounts() on the entry with the inode locked and then call d_delete() once the inode is unlocked. The thing is that between detach_mounts() and d_delete() the dentry is still hashed and positive. But after detach_mounts() nothing covers the dentry anymore. A lookup that finds this dentry in the dcache can uncover what the mounts hid. That's a problem when unlinking files or directories that are mountpoints in other mount namespaces. Everybody who had the underlying entry covered can race the detach_mount() call until d_delete() has run. The race window isn't all that small. It encompasses namespace_unlock() with a full synchronize_rcu_expedited() grace period and the inode_unlock() of the entry. In my experiments three walkers that kept trying read an overmounted file in 11938 of the 16140 unlinks that removed its mountpoint from a bind mount of the filesystem within a minute. Fun fact, d_invalidate() has the same ordering problem but gets it right. It unhashes the dentry first and detaches the mounts afterwards. Let's do the same in __detach_mounts(): - A lookup that hasn't found the dentry yet misses it in the dcache and waits for the directory lock that the caller holds until the name is gone for good. - A lockless lookup that found it already fails the mount_lock check while the dentry still counts as a mountpoint and the d_seq check once it doesn't, and retries. This fixes the lockless path. We still need to fix the reference count lookup in a follow-up patch. So d_drop() the dentry. The dentry stays positive and held but can't be found anymore. Then proceed with the detach and unlink. Reproducer: The reads were counted with the program below, three walkers for 60 s in a VM with 4 CPUs. The race window is stretched with the debug patch pasted here. fs.detach_race_walk_us sleeps in lookup_fast() once it found a mountpoint dentry and before its mounts are crossed. fs.detach_race_unlink_us sleeps in vfs_unlink() between detach_mounts() and d_delete(). // SPDX-License-Identifier: GPL-2.0 /* * unlink_covered: unlink a file that is a mountpoint in a detached copy of * its mount, against lookups that open it through that copy. * * A is a tmpfs with the file f1 (content SECRET_F) and the plain file * MARK_A. A' is an open_tree(OPEN_TREE_CLONE) copy of A with MARK_A bound * on A'/f1, held through an O_PATH fd on its root once the tree fd is * closed. Walkers open f1 through that fd while the driver unlinks A/f1, * where nothing is mounted on it. A walker may read MARK_A or get ENOENT. * A read of SECRET_F is a hit: the name was found after its mount was * gone. The lockless walks use openat2(RESOLVE_CACHED). * * usage: unlink_covered [-t seconds] [-w walkers] / #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif #include <errno.h> #include <fcntl.h> #include <pthread.h> #include <stdatomic.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/mount.h> #include <sys/stat.h> #include <sys/syscall.h> #include <linux/openat2.h> #ifndef __NR_open_tree #define __NR_open_tree 428 #endif #ifndef __NR_move_mount #define __NR_move_mount 429 #endif #ifndef __NR_openat2 #define __NR_openat2 437 #endif #ifndef OPEN_TREE_CLONE #define OPEN_TREE_CLONE 1 #endif #ifndef OPEN_TREE_CLOEXEC #define OPEN_TREE_CLOEXEC O_CLOEXEC #endif #ifndef MOVE_MOUNT_F_EMPTY_PATH #define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 #endif #define WORK "/tmp/uc" #define ADIR WORK "/A" static int duration = 60, nwalkers = 3; static atomic_int stop, writer_waiting; static pthread_rwlock_t cur_lock = PTHREAD_RWLOCK_INITIALIZER; static int cur_fd = -1; / the root of A', -1 wh ---truncated---
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/98xxx/CVE-2026-98981.json">CVE-2026-98981</a>
Reference	added	—	https://git.kernel.org/stable/c/528b383dc35d1e5caf64ddf5d35f983ae543b0d0
Reference	added	—	https://git.kernel.org/stable/c/8300de4aa5d09061bfcf2af5b52c0cdba3873185
Reference	added	—	https://git.kernel.org/stable/c/8d71bfc9b3fc15d7103e82ea9dc5057541866e46
Reference	added	—	https://git.kernel.org/stable/c/d29cd99db3db74cf3447be74d25740981789d461
Reference	added	—	https://git.kernel.org/stable/c/db90eecbde319527aa9480c039d32a0f5fe80574

Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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