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Linux KernelOperating system · Linux

CVE-2021-47012

HIGH · 7.8 CVSS v3.1 Published 2024-02-28
Fix available
A fix is available. Upgrade to 5.4.119 / 5.10.37 or later.
See remediation →
80/100
Remediation priority · High
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: RDMA/siw: Fix a use after free in siw_alloc_mr Our code analyzer reported a UAF. In siw_alloc_mr(), it calls siw_mr_add_mem(mr,..). In the implementation of siw_mr_add_mem(), mem is assigned to mr->mem and then mem is freed via kfree(mem) if xa_alloc_cyclic() failed. Here, mr->mem still point to a freed object. After, the execution continue up to the err_out branch of siw_alloc_mr, and the freed mr->mem is used in siw_mr_drop_mem(mr). My patch moves "mr->mem = mem" behind the if (xa_alloc_cyclic(..)<0) {} section, to avoid the uaf.

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-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free 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:>= 5.3, < 5.4.119>= 5.5, < 5.10.37>= 5.11, < 5.11.21>= 5.12, < 5.12.4

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 5.4.119 / 5.10.37 / 5.11.21 or later
Fixed in 5.4.1195.10.375.11.21
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to kernel version 5.4.119, 5.10.37, 5.11.21, or 5.12.4 (or later stable release) depending on your major version branch

  1. 1. Identify the currently running kernel version using `uname -r`
  2. 2. Check if the system is running an affected kernel version (5.3, 5.4.x before 5.4.119, 5.5-5.9.x, 5.10.x before 5.10.37, 5.11.x before 5.11.21, or 5.12.x before 5.12.4)
  3. 3. For enterprise Linux distributions (RHEL, CentOS, Ubuntu, Debian), check if a vendor kernel update is available via package manager (e.g., `yum update kernel`, `apt-get install linux-image-*`)
  4. 4. If running a distribution kernel, apply the vendor-provided security update which includes the fix for this CVE
  5. 5. If running a custom or upstream kernel, apply the fix from commit 3093ee182f01689b89e9f8797b321603e5de4f63 to the siw_mr_add_mem() function in drivers/infiniband/sw/siw/siw_mem.c: move the assignment `mr->mem = mem` after the `if (xa_alloc_cyclic(...)<0)` block to prevent the use-after-free when xa_alloc_cyclic fails
  6. 6. Reboot the system into the updated/patched kernel
Caveat Kernel upgrades may require rebooting and could introduce compatibility changes with out-of-tree modules or specific hardware drivers; test thoroughly in a non-production environment first

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 $3,200. 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-2021-47012 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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