Unknown

CVE-2025-40072 — fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing

In the Linux kernel, the following vulnerability has been resolved: fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing The function do_fanotify_mark() does not validate if mnt_ns_from_dentry() returns NULL before dereferencing mntns->user_ns. This causes a NULL pointer dereference in do_fanotify_mark() if the path is not a mount namespace object. Fix this by checking mnt_ns_from_dentry()'s return value before dereferencing it. Before the patch $ gcc fanotify_nullptr.c -o fanotify_nullptr $ mkdir A $ ./fanotify_nullptr Fanotify fd: 3 fanotify_mark: Operation not permitted $ unshare -Urm Fanotify fd: 3 Killed int main(void){ int ffd; ffd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_MNT, 0); if(ffd < 0){ perror("fanotify_init"); exit(EXIT_FAILURE); } printf("Fanotify fd: %d\n",ffd); if(fanotify_mark(ffd, FAN_MARK_ADD | FAN_MARK_MNTNS, FAN_MNT_ATTACH, AT_FDCWD, "A") < 0){ perror("fanotify_mark"); exit(EXIT_FAILURE); } return 0; } After the patch $ gcc fanotify_nullptr.c -o fanotify_nullptr $ mkdir A $ ./fanotify_nullptr Fanotify fd: 3 fanotify_mark: Operation not permitted $ unshare -Urm Fanotify fd: 3 fanotify_mark: Invalid argument [ 25.694973] BUG: kernel NULL pointer dereference, address: 0000000000000038 [ 25.695006] #PF: supervisor read access in kernel mode [ 25.695012] #PF: error_code(0x0000) - not-present page [ 25.695017] PGD 109a30067 P4D 109a30067 PUD 142b46067 PMD 0 [ 25.695025] Oops: Oops: 0000 [#1] SMP NOPTI [ 25.695032] CPU: 4 UID: 1000 PID: 1478 Comm: fanotify_nullpt Not tainted 6.17.0-rc4 #1 PREEMPT(lazy) [ 25.695040] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 [ 25.695049] RIP: 0010:do_fanotify_mark+0x817/0x950 [ 25.695066] Code: 04 00 00 e9 45 fd ff ff 48 8b 7c 24 48 4c 89 54 24 18 4c 89 5c 24 10 4c 89 0c 24 e8 b3 11 fc ff 4c 8b 54 24 18 4c 8b 5c 24 10 <48> 8b 78 38 4c 8b 0c 24 49 89 c4 e9 13 fd ff ff 8b 4c 24 28 85 c9 [ 25.695081] RSP: 0018:ffffd31c469e3c08 EFLAGS: 00010203 [ 25.695104] RAX: 0000000000000000 RBX: 0000000001000000 RCX: ffff8eb48aebd220 [ 25.695110] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8eb4835e8180 [ 25.695115] RBP: 0000000000000111 R08: 0000000000000000 R09: 0000000000000000 [ 25.695142] R10: ffff8eb48a7d56c0 R11: ffff8eb482bede00 R12: 00000000004012a7 [ 25.695148] R13: 0000000000000110 R14: 0000000000000001 R15: ffff8eb48a7d56c0 [ 25.695154] FS: 00007f8733bda740(0000) GS:ffff8eb61ce5f000(0000) knlGS:0000000000000000 [ 25.695162] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 25.695170] CR2: 0000000000000038 CR3: 0000000136994006 CR4: 00000000003706f0 [ 25.695201] Call Trace: [ 25.695209] <TASK> [ 25.695215] __x64_sys_fanotify_mark+0x1f/0x30 [ 25.695222] do_syscall_64+0x82/0x2c0 ...

Published Oct 28, 2025 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.18%

ahead of 7% of scored CVEs · Oct 14, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 58f5fbeb367ff6f30a2448b2cad70f70b2de4b06 and < 73ce2a774ad6497cbd48dc4f8a5d699bc417f3fa≥ 58f5fbeb367ff6f30a2448b2cad70f70b2de4b06 and < 62e59ffe8787b5550ccff70c30b6f6be6a3ac3ddversion 6.16	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.18%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 13, 2026
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
2025
CVE published
Oct 28, 2025 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

2 on the record

git.kernel.org/stable/c/73ce2a774ad6497cbd48dc4f8a5d699bc417f3fa
NIST National Vulnerability Database
git.kernel.org/stable/c/62e59ffe8787b5550ccff70c30b6f6be6a3ac3dd
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 14h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 14h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-40072 is "fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.18% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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