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Linux KernelOperating system · Linux

CVE-2021-47631

MEDIUM · 5.5 CVSS v3.1 Published 2025-02-26
Fix available
A fix is available. Upgrade to 4.9.311 / 4.14.276 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: ARM: davinci: da850-evm: Avoid NULL pointer dereference With newer versions of GCC, there is a panic in da850_evm_config_emac() when booting multi_v5_defconfig in QEMU under the palmetto-bmc machine: Unable to handle kernel NULL pointer dereference at virtual address 00000020 pgd = (ptrval) [00000020] *pgd=00000000 Internal error: Oops: 5 [#1] PREEMPT ARM Modules linked in: CPU: 0 PID: 1 Comm: swapper Not tainted 5.15.0 #1 Hardware name: Generic DT based system PC is at da850_evm_config_emac+0x1c/0x120 LR is at do_one_initcall+0x50/0x1e0 The emac_pdata pointer in soc_info is NULL because davinci_soc_info only gets populated on davinci machines but da850_evm_config_emac() is called on all machines via device_initcall(). Move the rmii_en assignment below the machine check so that it is only dereferenced when running on a supported SoC.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-476

The code follows a pointer that is null, crashing the process. An attacker who can reliably trigger it turns the crash into a denial of service. The fix is checking for null before use and handling the failure path gracefully.

General guidance for the null pointer dereference class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.33, < 4.9.311>= 4.10, < 4.14.276>= 4.15, < 4.19.239>= 4.20, < 5.4.190>= 5.5, < 5.10.112>= 5.11, < 5.15.35>= 5.16, < 5.17.4= 5.18

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.9.311 / 4.14.276 / 4.19.239 or later
Fixed in 4.9.3114.14.2764.19.239
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to Linux kernel 4.9.311+, 4.14.276+, 4.19.239+, or 5.4.190+ (preferably 5.10.x/5.15.x LTS for long-term support)

  1. Identify the current running Linux kernel version using 'uname -r' or 'cat /proc/version'
  2. Compare the current version against the vulnerable ranges: < 4.9.311, 4.10.x - 4.14.275, 4.15.x - 4.19.238, or 4.20.x - 5.4.189
  3. If running a vulnerable version, plan for a kernel upgrade to a fixed release
  4. Upgrade the Linux kernel to version 4.9.311 or later (if on 4.9.x), 4.14.276 or later (if on 4.14.x), 4.19.239 or later (if on 4.19.x), or 5.4.190 or later (if on 5.4.x or earlier)
  5. For long-term stability, consider upgrading to 5.10.x, 5.15.x, or later stable releases which include the fix
  6. After upgrade, verify the fix is present by checking the da850-evm.c file contains the machine check before dereferencing emac_pdata, or confirm the kernel version includes commit 0940795c6834fbe7705acc5c3d4b2f7a5f67527a
Caveat Kernel upgrade carries standard risk; ensure compatibility with custom drivers/modules and test in staging before production deployment. The underlying davinci platform support may require specific device tree configurations.

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $2,850. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-47631 in production — separate from our analysis above.

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What this is

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  • Version or environment caveats, and links to real fixes
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