Not ratedCVE-2023-54271

Linux Kernel: NULL Pointer Dereference (CVE-2023-54271)

Published 30.12.2025Last modified 15.10.2026Sources: SUSE, Debian LTS, BSI, Siemens ProductCERT, Ubuntu, Red Hat, CVE.org, EUVD

What is affected, what to do

Update Linux Kernel to version 5.15.210, Linux Kernel to version 6.1.176, Linux Kernel to version 6.4.16.

Affected: Linux Kernel lt 5.4..5.15.210
Linux Kernel lt 5.16..6.1.176
Linux Kernel lt 6.2..6.4.16
Linux Kernel lt 6.5..6.5.3
Fixed in: Linux Kernel 5.15.210
Linux Kernel 6.1.176
Linux Kernel 6.4.16
Linux Kernel 6.5.3
Linux Kernel 6.6

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Metrics

—

Priority

No value is available for this vulnerability.

0.0

CVSS v3

Severity Not rated on the scale from 0 to 10.

Source: SUSE, Debian LTS, BSI, Siemens ProductCERT, Ubuntu, Red Hat, CVE.org, EUVD

0.2 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 11.7

Show all metrics

Severity: Not rated
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: 14.21 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
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: 0.0
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: 11.7; 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: 30.12.2025

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:

blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init

blk-iocost sometimes causes the following crash:

BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... RIP: 0010:_raw_spin_lock+0x17/0x30 Code: be 01 02 00 00 e8 79 38 39 ff 31 d2 89 d0 5d c3 0f 1f 00 0f 1f 44 00 00 55 48 89 e5 65 ff 05 48 d0 34 7e b9 01 00 00 00 31 c0 0f b1 0f 75 02 5d c3 89 c6 e8 ea 04 00 00 5d c3 0f 1f 84 00 00 RSP: 0018:ffffc900023b3d40 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 00000000000000e0 RCX: 0000000000000001 RDX: ffffc900023b3d20 RSI: ffffc900023b3cf0 RDI: 00000000000000e0 RBP: ffffc900023b3d40 R08: ffffc900023b3c10 R09: 0000000000000003 R10: 0000000000000064 R11: 000000000000000a R12: ffff888102337000 R13: fffffffffffffff2 R14: ffff88810af408c8 R15: ffff8881070c3600 FS: 00007faaaf364fc0(0000) GS:ffff88842fdc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000e0 CR3: 00000001097b1000 CR4: 0000000000350ea0 Call Trace: ioc_weight_write+0x13d/0x410 cgroup_file_write+0x7a/0x130 kernfs_fop_write_iter+0xf5/0x170 vfs_write+0x298/0x370 ksys_write+0x5f/0xb0 __x64_sys_write+0x1b/0x20 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0

This happens because iocg->ioc is NULL. The field is initialized by ioc_pd_init() and never cleared. The NULL deref is caused by blkcg_activate_policy() installing blkg_policy_data before initializing it.

blkcg_activate_policy() was doing the following:

Allocate pd's for all existing blkg's and install them in blkg->pd[].
Initialize all pd's.
Online all pd's.

blkcg_activate_policy() only grabs the queue_lock and may release and re-acquire the lock as allocation may need to sleep. ioc_weight_write() grabs blkcg->lock and iterates all its blkg's. The two can race and if ioc_weight_write() runs during #1 or between #1 and #2, it can encounter a pd which is not initialized yet, leading to crash.

The crash can be reproduced with the following script:

#!/bin/bash

echo +io > /sys/fs/cgroup/cgroup.subtree_control systemd-run --unit touch-sda --scope dd if=/dev/sda of=/dev/null bs=1M count=1 iflag=direct echo 100 > /sys/fs/cgroup/system.slice/io.weight bash -c "echo '8:0 enable=1' > /sys/fs/cgroup/io.cost.qos" & sleep .2 echo 100 > /sys/fs/cgroup/system.slice/io.weight

with the following patch applied:

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index fc49be622e05..38d671d5e10c 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1553,6 +1553,12 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol) pd->online = false; }
  if (system_state == SYSTEM_RUNNING) {
          spin_unlock_irq(&q->queue_lock);
          ssleep(1);
          spin_lock_irq(&q->queue_lock);
  }
/* all allocated, init in the same order */ if (pol->pd_init_fn) list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)

I don't see a reason why all pd's should be allocated, initialized and onlined together. The only ordering requirement is that parent blkgs to be initialized and onlined before children, which is guaranteed from the walking order. Let's fix the bug by allocating, initializing and onlining pd for each blkg and holding blkcg->lock over initialization and onlining. This ensures that an installed blkg is always fully initialized and onlined removing the the race window.

Source: suse_csaf, Debian LTS Advisories, BSI WID Portal, BSI CSAF, siemens_advisory, Ubuntu Security Notices, redhat_csaf, cvelistv5, NVD (NIST), ENISA EUVD

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	`6.5 – < 6.5.3` `—` `5.4 – < 5.15.210` `5.16 – < 6.1.176` `6.2 – < 6.4.16`	`6.5.3` `6.6` `5.15.210` `6.1.176` `6.4.16`
IBM	DataPower Gateway	`10.6.0.0-10.6.0.8` `10.5.0.0-10.5.0.20`	— —
Siemens	SIMATIC S7	`1500 TM MFP V1.1.1 GNU/Linux subsystem`	—

Vendors and products

Affected operating systems

Affected operating systems

Linux	debian	linux	`bookworm`
Linux	debian	linux-6.1	`bullseye`
Linux	ubuntu	linux-gcp-5.15	`focal`

References & sources

git.kernel.orgstable/c/e39ef7880d1057b2ebcdb013405f4d84a257db23euvd
git.kernel.orgstable/c/7d63c6f9765339dcfc34b7365ced7c518012e4feeuvd
git.kernel.orgstable/c/ec14a87ee1999b19d8b7ed0fa95fea80644624aeeuvd
git.kernel.orgstable/c/da6cc648c1f570290af1ddbe6b7ca3d91b1d6db9
git.kernel.orgstable/c/33f0370bb7ce15a59d72a4d8a05421d334a04add
Siemens ProductCERTproductcert/html/ssa-784472.html

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).

15.10.2026Record modifiedLinux

New references:

and 1 more reference

Show 10 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://git.kernel.org/stable/c/33f0370bb7ce15a59d72a4d8a05421d334a04add
Reference	added	—	https://git.kernel.org/stable/c/7d63c6f9765339dcfc34b7365ced7c518012e4fe
Reference	added	—	https://git.kernel.org/stable/c/da6cc648c1f570290af1ddbe6b7ca3d91b1d6db9
Reference	added	—	https://git.kernel.org/stable/c/e39ef7880d1057b2ebcdb013405f4d84a257db23
Reference	added	—	https://git.kernel.org/stable/c/ec14a87ee1999b19d8b7ed0fa95fea80644624ae
Reference	removed	https://git.kernel.org/stable/c/33f0370bb7ce15a59d72a4d8a05421d334a04add	—
Reference	removed	https://git.kernel.org/stable/c/7d63c6f9765339dcfc34b7365ced7c518012e4fe	—
Reference	removed	https://git.kernel.org/stable/c/da6cc648c1f570290af1ddbe6b7ca3d91b1d6db9	—
Reference	removed	https://git.kernel.org/stable/c/e39ef7880d1057b2ebcdb013405f4d84a257db23	—
Reference	removed	https://git.kernel.org/stable/c/ec14a87ee1999b19d8b7ed0fa95fea80644624ae	—

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

15.10.2026Record modifiedSiemens ADP

New references:

https://cert-portal.siemens.com/productcert/html/ssa-784472.html

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2023/54xxx/CVE-2023-54271.json">CVE-2023-54271</a>
Reference	added	—	https://cert-portal.siemens.com/productcert/html/ssa-784472.html

Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

19.06.2026Record modifiedLinux

New references:

Show 3 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://git.kernel.org/stable/c/33f0370bb7ce15a59d72a4d8a05421d334a04add
Reference	added	—	https://git.kernel.org/stable/c/da6cc648c1f570290af1ddbe6b7ca3d91b1d6db9
Affected versions (publisher)	changed	Linux, Linux	Linux, Linux

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

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