# CVE-2026-31686

> Vulnerability · severity: **HIGH** (CVSS 7.8).

## Description

In the Linux kernel, the following vulnerability has been resolved:

mm/kasan: fix double free for kasan pXds

kasan_free_pxd() assumes the page table is always struct page aligned. 
But that's not always the case for all architectures.  E.g.  In case of
powerpc with 64K pagesize, PUD table (of size 4096) comes from slab cache
named pgtable-2^9.  Hence instead of page_to_virt(pxd_page()) let's just
directly pass the start of the pxd table which is passed as the 1st
argument.

This fixes the below double free kasan issue seen with PMEM:

radix-mmu: Mapped 0x0000047d10000000-0x0000047f90000000 with 2.00 MiB pages
==================================================================
BUG: KASAN: double-free in kasan_remove_zero_shadow+0x9c4/0xa20
Free of addr c0000003c38e0000 by task ndctl/2164

CPU: 34 UID: 0 PID: 2164 Comm: ndctl Not tainted 6.19.0-rc1-00048-gea1013c15392 #157 VOLUNTARY
Hardware name: IBM,9080-HEX POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.00 (NH1060_012) hv:phyp pSeries
Call Trace:
 dump_stack_lvl+0x88/0xc4 (unreliable)
 print_report+0x214/0x63c
 kasan_report_invalid_free+0xe4/0x110
 check_slab_allocation+0x100/0x150
 kmem_cache_free+0x128/0x6e0
 kasan_remove_zero_shadow+0x9c4/0xa20
 memunmap_pages+0x2b8/0x5c0
 devm_action_release+0x54/0x70
 release_nodes+0xc8/0x1a0
 devres_release_all+0xe0/0x140
 device_unbind_cleanup+0x30/0x120
 device_release_driver_internal+0x3e4/0x450
 unbind_store+0xfc/0x110
 drv_attr_store+0x78/0xb0
 sysfs_kf_write+0x114/0x140
 kernfs_fop_write_iter+0x264/0x3f0
 vfs_write+0x3bc/0x7d0
 ksys_write+0xa4/0x190
 system_call_exception+0x190/0x480
 system_call_vectored_common+0x15c/0x2ec
---- interrupt: 3000 at 0x7fff93b3d3f4
NIP:  00007fff93b3d3f4 LR: 00007fff93b3d3f4 CTR: 0000000000000000
REGS: c0000003f1b07e80 TRAP: 3000   Not tainted  (6.19.0-rc1-00048-gea1013c15392)
MSR:  800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 48888208  XER: 00000000
<...>
NIP [00007fff93b3d3f4] 0x7fff93b3d3f4
LR [00007fff93b3d3f4] 0

## Key facts

- **CVE ID:** CVE-2026-31686
- **Published:** 2026-04-27
- **CVSS severity:** HIGH
- **CVSS base score:** 7.8
- **CWE codes:** CWE-415

## Affected products

- `linux:linux_kernel`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31686

## Citation

> AI Analytics. CVE-2026-31686. Retrieved 2026-07-27 from https://api.ai-analytics.org/cve/CVE-2026-31686. Derived from NIST NVD. Licensed CC0.

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