SB20260916130 - Improper control of a resource through its lifetime in Linux kernel mm

Description

This security bulletin contains information about 1 vulnerability.

1) Improper control of a resource through its lifetime (CVE-ID: CVE-2026-89987)

CWE-ID: CWE-664 - Improper control of a resource through its lifetime

CVSSv4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to cause silent data loss.

The vulnerability exists due to failure to propagate the PMD dirty bit in zap_huge_pmd_folio() when unmapping a PMD-mapped MAP_SHARED tmpfs mapping after data has been written through a read-faulted mapping. A local user can write data through a shared tmpfs mapping and unmap it to cause silent data loss.

Exploitation requires shmem transparent huge pages and swap to be enabled.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/9435cddf1378d149d826bd7bd1448a44bf96868d
• https://git.kernel.org/stable/c/effe3cc6d4fdd407457eb30f7b0ef094393f0d64
• https://git.kernel.org/stable/c/fe6cf984939d8e12cb33a99673c8d026c5135e68