High

CVE-2025-40271 — fs/proc: fix uaf in proc_readdir_de()

In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix uaf in proc_readdir_de() Pde is erased from subdir rbtree through rb_erase(), but not set the node to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE() set the erased node to EMPTY, then pde_subdir_next() will return NULL to avoid uaf access. We found an uaf issue while using stress-ng testing, need to run testcase getdent and tun in the same time. The steps of the issue is as follows: 1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current pde is tun3; 2) in the [time windows] unregister netdevice tun3 and tun2, and erase them from rbtree. erase tun3 first, and then erase tun2. the pde(tun2) will be released to slab; 3) continue to getdent process, then pde_subdir_next() will return pde(tun2) which is released, it will case uaf access. CPU 0 | CPU 1 ------------------------------------------------------------------------- traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2 sys_getdents64() | iterate_dir() | proc_readdir() | proc_readdir_de() | snmp6_unregister_dev() pde_get(de); | proc_remove() read_unlock(&proc_subdir_lock); | remove_proc_subtree() | write_lock(&proc_subdir_lock); [time window] | rb_erase(&root->subdir_node, &parent->subdir); | write_unlock(&proc_subdir_lock); read_lock(&proc_subdir_lock); | next = pde_subdir_next(de); | pde_put(de); | de = next; //UAF | rbtree of dev_snmp6 | pde(tun3) / \ NULL pde(tun2)

Published Dec 6, 2025 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · 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.

Exploit-DB · 1

How the score was calculated

Public exploit/PoC (exploitdb)+8
EPSS 0.5% (30-day exploitation probability)+6
Technical severity (high)+6

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

0.46%

ahead of 38% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

7.8

High · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

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	≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 1d1596d68a6f11d28f677eedf6cf5b17dbfeb491≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < c81d0385500446efe48c305bbb83d47f2ae23a50≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 4cba73c4c89219beef7685a47374bf88b1022369≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 6f2482745e510ae1dacc9b090194b9c5f918d774≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 67272c11f379d9aa5e0f6b16286b9d89b3f76046≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 623bb26127fb581a741e880e1e1a47d79aecb6f8≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 03de7ff197a3d0e17d0d5c58fdac99a63cba8110≥ 710585d4922fd315f2cada8fbe550ae8ed23e994 and < 895b4c0c79b092d732544011c3cecaf7322c36a1 and 1 more version 3.19	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.8	CVSS 3.1	High	1.8	5.9	416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
7.8	CVSS 3.1	High	—	—	GitHub, Inc. via GitHub Security Advisories
7.8	CVSS 3.1	High	—	—	Linux via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Exploit-DB

Linux Kernel proc_readdir_de() 6.18-rc5 - Local Privilege Escalation May 4, 2026

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.46%

Detection

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

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 7.8
Oct 13, 2026 · NIST National Vulnerability Database
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
Dec 6, 2025 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 15, 2026 – Oct 15, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

11 on the record

git.kernel.org/stable/c/623bb26127fb581a741e880e1e1a47d79aecb6f8
NIST National Vulnerability Database
git.kernel.org/stable/c/03de7ff197a3d0e17d0d5c58fdac99a63cba8110
NIST National Vulnerability Database
github.com/advisories/GHSA-r37x-wmxh-7hvh
GitHub Security Advisories
git.kernel.org/stable/c/67272c11f379d9aa5e0f6b16286b9d89b3f76046
NIST National Vulnerability Database
git.kernel.org/stable/c/4cba73c4c89219beef7685a47374bf88b1022369
NIST National Vulnerability Database
git.kernel.org/stable/c/c81d0385500446efe48c305bbb83d47f2ae23a50
NIST National Vulnerability Database
git.kernel.org/stable/c/1d1596d68a6f11d28f677eedf6cf5b17dbfeb491
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2025-40271
GitHub Security Advisories
git.kernel.org/stable/c/6f2482745e510ae1dacc9b090194b9c5f918d774
NIST National Vulnerability Database
git.kernel.org/stable/c/895b4c0c79b092d732544011c3cecaf7322c36a1
NIST National Vulnerability Database
cert-portal.siemens.com/productcert/html/ssa-253495.html
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 6h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 6h
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 fixed version, patch or mitigation documented.
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-2025-40271 is "fs/proc: fix uaf in proc_readdir_de()", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.8 describes technical severity. EPSS 0.46% 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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