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Linux KernelOperating system · Linux

CVE-2026-53343

MEDIUM · 5.5 CVSS v3.1 Published 2026-07-01
Fix available
A fix is available. Upgrade to 6.1.176 / 6.6.143 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available 7 weeks old

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: 9475/1: entry: use byte load for KASAN VMAP stack shadow Commit 44e9a3bb76e5 ("ARM: 9430/1: entry: Do a dummy read from VMAP shadow") added a dummy read from the KASAN VMAP stack shadow in __switch_to(). The read uses ldr, but the KASAN shadow address is byte-granular and is not guaranteed to be word aligned. ARMv5 faults unaligned word loads. With CONFIG_KASAN_VMALLOC and CONFIG_VMAP_STACK enabled, ARM926/VersatilePB crashes in __switch_to() with an alignment exception before reaching init. Use ldrb for the dummy shadow access. The code only needs to fault in the shadow mapping if the stack shadow is missing, so a byte load is sufficient and matches the granularity of KASAN shadow memory.

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 · high confidence

On ARM, the __switch_to() function performs a dummy read from KASAN VMAP stack shadow using 'ldr' (word load). However, KASAN shadow addresses are byte-granular and not word-aligned. ARMv5 processors like ARM926 fault on unaligned word loads when CONFIG_KASAN_VMALLOC and CONFIG_VMAP_STACK are enabled, causing a crash before init.

MitigationReplace the 'ldr' instruction with 'ldrb' (byte load) in __switch_to() to match KASAN's byte-granular shadow memory. This is a single-instruction change in arch/arm/kernel/entry-armv.S.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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:>= 6.1.120, < 6.1.176>= 6.6.64, < 6.6.143>= 6.12.4, < 6.12.94>= 6.13, < 6.18.36>= 6.19, < 7.0.13= 7.1

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check kernel version
    Run 'uname -r' or 'cat /proc/version' to get the installed kernel version
    Affected if Version falls within >= 6.1.120 && < 6.1.176, OR >= 6.6.64 && < 6.6.143, OR >= 6.12.4 && < 6.12.94, OR >= 6.13 && < 6.18.36, OR >= 6.19 && < 7.0.13, OR == 7.1
  2. Confirm ARMv5 architecture
    Check /proc/cpuinfo for 'Processor' or 'CPU architecture' showing ARMv5 or ARM926, or check device tree
    Affected if Running on ARMv5 (ARM926) processor
  3. Verify CONFIG_KASAN_VMALLOC is enabled
    Check kernel config file (e.g., /boot/config-* or /proc/config.gz) for 'CONFIG_KASAN_VMALLOC=y'
    Affected if CONFIG_KASAN_VMALLOC is set to y in the kernel configuration
  4. Verify CONFIG_VMAP_STACK is enabled
    Check kernel config file for 'CONFIG_VMAP_STACK=y'
    Affected if CONFIG_VMAP_STACK is set to y in the kernel configuration
  5. Inspect __switch_to() for ldr instruction
    Examine the arch/arm/kernel/entry-armv.S or equivalent source file in __switch_to() function where KASAN shadow is accessed; search for 'ldr' accessing KASAN shadow in the stack switching code
    Affected if The code uses 'ldr' (word load) instead of 'ldrb' (byte load) to access KASAN shadow memory in __switch_to()

User is affected if running an affected kernel version on ARMv5 with both CONFIG_KASAN_VMALLOC and CONFIG_VMAP_STACK enabled, and the __switch_to() function still uses 'ldr' instead of 'ldrb' for KASAN shadow access.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 6.1.176 / 6.6.143 / 6.12.94 or later
Fixed in 6.1.1766.6.1436.12.94
Vendor patch git.kernel.org →
Interim mitigation

Replace the 'ldr' instruction with 'ldrb' (byte load) in __switch_to() to match KASAN's byte-granular shadow memory. This is a single-instruction change in arch/arm/kernel/entry-armv.S.

Recommended fix High confidence

Linux Kernel 6.1.176, 6.6.143, 6.12.94, or 6.18.36 and later

  1. Identify the file containing the __switch_to() function for ARM (typically arch/arm/kernel/entry.S or similar)
  2. Locate the dummy read from KASAN VMAP stack shadow that uses 'ldr' instruction
  3. Change 'ldr' to 'ldrb' for the KASAN shadow access to use byte-granular load instead of word-aligned load
  4. Rebuild the kernel with CONFIG_KASAN_VMALLOC and CONFIG_VMAP_STACK enabled for ARM targets
  5. Test on ARM926/VersatilePB hardware or QEMU emulation to verify the alignment fault is resolved
Caveat Minimal risk - this is a targeted fix for ARM alignment handling; the change from ldr to ldrb only affects KASAN shadow access behavior and does not change functional behavior for correctly aligned addresses

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

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
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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-2026-53343 in production — separate from our analysis above.

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