Linux KernelOperating system · Linux
CVE-2021-46994
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 · uneditedIn the Linux kernel, the following vulnerability has been resolved: can: mcp251x: fix resume from sleep before interface was brought up Since 8ce8c0abcba3 the driver queues work via priv->restart_work when resuming after suspend, even when the interface was not previously enabled. This causes a null dereference error as the workqueue is only allocated and initialized in mcp251x_open(). To fix this we move the workqueue init to mcp251x_can_probe() as there is no reason to do it later and repeat it whenever mcp251x_open() is called. [mkl: fix error handling in mcp251x_stop()]
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 analysisThe 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
>= 5.5, < 5.10.38>= 5.11, < 5.11.22>= 5.12, < 5.12.5CVSS 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 · scoped5.10.385.11.225.12.5
Linux Kernel 5.10.38, 5.11.22, or 5.12.5 (or any later stable release)
- Identify the Linux kernel source or build configuration in use and confirm it matches one of the affected version ranges (5.5 to 5.10.37, 5.11 to 5.11.21, or 5.12 to 5.12.4)
- Obtain the vendor patch from commit 03c427147b2d3e503af258711af4fc792b89b0af (https://git.kernel.org/stable/c/03c427147b2d3e503af258711af4fc792b89b0af)
- Apply the patch to the kernel source, which moves the workqueue initialization from mcp251x_open() to mcp251x_can_probe() to ensure the workqueue exists before any resume operation attempts to use it
- Rebuild the kernel with the patched mcp251x driver
- Reboot the system with the patched kernel
- Alternatively, upgrade the kernel to a fixed release: 5.10.38 or later, 5.11.22 or later, or 5.12.5 or later
Generated from the published advisory — verify against the referenced sources before acting.
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Free · runs locallyCheck whether your project pulls in CVE-2021-46994 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-46994 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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