# CVE-2021-47440: net: encx24j600: check error in devm_regmap_init_encx24j600

> A missing error check in the encx24j600 network driver can cause a null pointer dereference, leading to a system crash.

- **Severity:** Low 2.3 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47440, GHSA-h8c2-87vw-jwfw, UBUNTU-CVE-2021-47440

## What is CVE-2021-47440?

CVE-2021-47440 is a low-severity vulnerability in Linux kernel, published on 22 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net: encx24j600: check error in devm_regmap_init_encx24j600

devm_regmap_init may return error which caused by like out of memory,
this will results in null pointer dereference later when reading
or writing register:

general protection fault in encx24j600_spi_probe
KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097]
CPU: 0 PID: 286 Comm: spi-encx24j600- Not tainted 5.15.0-rc2-00142-g9978db750e31-dirty #11 9c53a778c1306b1b02359f3c2bbedc0222cba652
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:regcache_cache_bypass drivers/base/regmap/regcache.c:540
Code: 54 41 89 f4 55 53 48 89 fb 48 83 ec 08 e8 26 94 a8 fe 48 8d bb a0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 4a 03 00 00 4c 8d ab b0 00 00 00 48 8b ab a0 00
RSP: 0018:ffffc900010476b8 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: fffffffffffffff4 RCX: 0000000000000000
RDX: 0000000000000012 RSI: ffff888002de0000 RDI: 0000000000000094
RBP: ffff888013c9a000 R08: 0000000000000000 R09: fffffbfff3f9cc6a
R10: ffffc900010476e8 R11: fffffbfff3f9cc69 R12: 0000000000000001
R13: 000000000000000a R14: ffff888013c9af54 R15: ffff888013c9ad08
FS:  00007ffa984ab580(0000) GS:ffff88801fe00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055a6384136c8 CR3: 000000003bbe6003 CR4: 0000000000770ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 encx24j600_spi_probe drivers/net/ethernet/microchip/encx24j600.c:459
 spi_probe drivers/spi/spi.c:397
 really_probe drivers/base/dd.c:517
 __driver_probe_device drivers/base/dd.c:751
 driver_probe_device drivers/base/dd.c:782
 __device_attach_driver drivers/base/dd.c:899
 bus_for_each_drv drivers/base/bus.c:427
 __device_attach drivers/base/dd.c:971
 bus_probe_device drivers/base/bus.c:487
 device_add drivers/base/core.c:3364
 __spi_add_device drivers/spi/spi.c:599
 spi_add_device drivers/spi/spi.c:641
 spi_new_device drivers/spi/spi.c:717
 new_device_store+0x18c/0x1f1 [spi_stub 4e02719357f1ff33f5a43d00630982840568e85e]
 dev_attr_store drivers/base/core.c:2074
 sysfs_kf_write fs/sysfs/file.c:139
 kernfs_fop_write_iter fs/kernfs/file.c:300
 new_sync_write fs/read_write.c:508 (discriminator 4)
 vfs_write fs/read_write.c:594
 ksys_write fs/read_write.c:648
 do_syscall_64 arch/x86/entry/common.c:50
 entry_SYSCALL_64_after_hwframe arch/x86/entry/entry_64.S:113

Add error check in devm_regmap_init_encx24j600 to avoid this situation.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-47440?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47440?

Apply the vendor's patch.

## Is CVE-2021-47440 being exploited?

There is no known exploitation of CVE-2021-47440 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47440 and fix it if it is affected.

What it is: CVE-2021-47440 is a low-severity vulnerability in Linux kernel, published on 22 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-47440 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-47440/ (Markdown: https://insights.sbomify.com/CVE-2021-47440/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47440
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47440
- OSV: https://osv.dev/vulnerability/CVE-2021-47440

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47440/
Summaries are generated and may contain mistakes; the official description above is the record.