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Linux KernelOperating system · Linux

CVE-2026-31438

MEDIUM · 5.5 CVSS v3.1 Published 2026-04-22
Fix available
A fix is available. Upgrade to 6.12.80 / 6.18.21 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: netfs: Fix kernel BUG in netfs_limit_iter() for ITER_KVEC iterators When a process crashes and the kernel writes a core dump to a 9P filesystem, __kernel_write() creates an ITER_KVEC iterator. This iterator reaches netfs_limit_iter() via netfs_unbuffered_write(), which only handles ITER_FOLIOQ, ITER_BVEC and ITER_XARRAY iterator types, hitting the BUG() for any other type. Fix this by adding netfs_limit_kvec() following the same pattern as netfs_limit_bvec(), since both kvec and bvec are simple segment arrays with pointer and length fields. Dispatch it from netfs_limit_iter() when the iterator type is ITER_KVEC.

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:>= 6.8, < 6.12.80>= 6.13, < 6.18.21>= 6.19, < 6.19.11= 7.0

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 6.12.80 / 6.18.21 / 6.19.11 or later
Fixed in 6.12.806.18.216.19.11
Vendor patch git.kernel.org →
Recommended fix High confidence

6.12.80, 6.18.21, or 6.19.11 (depending on which branch you are on); for 7.0 apply vendor patch

  1. 1. Identify the current running kernel version using `uname -r`
  2. 2. Determine which affected version range your kernel falls into (>= 6.8 && < 6.12.80, >= 6.13 && < 6.18.21, >= 6.19 && < 6.19.11, or 7.0)
  3. 3. For kernels 6.12.x: upgrade to kernel version 6.12.80 or later
  4. 4. For kernels 6.13.x through 6.17.x: upgrade to kernel version 6.18.21 or later
  5. 5. For kernels 6.19.x: upgrade to kernel version 6.19.11 or later
  6. 6. For kernel 7.0: apply vendor patch commit 00d6df7115f6972370974212de9088087820802e or wait for 7.0.x fix
  7. 7. Reboot into the patched kernel
  8. 8. Verify the fix is applied by checking the netfs_limit_iter function includes ITER_KVEC handling
Caveat Kernel upgrades carry inherent risk; ensure compatibility with userspace tools and drivers before production deployment

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-2026-31438 in production — separate from our analysis above.

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What this is

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