Linux Distros Unpatched Vulnerability : CVE-2025-39992

critical Nessus Plugin ID 271534

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Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- mm: swap: check for stable address space before operating on the VMA It is possible to hit a zero entry while traversing the vmas in unuse_mm() called from swapoff path and accessing it causes the OOPS: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000446--> Loading the memory from offset 0x40 on the XA_ZERO_ENTRY as address. Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault The issue is manifested from the below race between the fork() on a process and swapoff: fork(dup_mmap()) swapoff(unuse_mm) --------------- ----------------- 1) Identical mtree is built using __mt_dup(). 2) copy_pte_range()--> copy_nonpresent_pte(): The dst mm is added into the mmlist to be visible to the swapoff operation. 3) Fatal signal is sent to the parent process(which is the current during the fork) thus skip the duplication of the vmas and mark the vma range with XA_ZERO_ENTRY as a marker for this process that helps during exit_mmap(). 4) swapoff is tried on the 'mm' added to the 'mmlist' as part of the 2. 5) unuse_mm(), that iterates through the vma's of this 'mm' will hit the non-NULL zero entry and operating on this zero entry as a vma is resulting into the oops. The proper fix would be around not exposing this partially-valid tree to others when droping the mmap lock, which is being solved with [1]. A simpler solution would be checking for MMF_UNSTABLE, as it is set if mm_struct is not fully initialized in dup_mmap(). Thanks to Liam/Lorenzo/David for all the suggestions in fixing this issue. (CVE-2025-39992)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Critical

ID: 271534

File Name: unpatched_CVE_2025_39992.nasl

Version: 1.1

Type: local

Agent: unix

Family: Misc.

Published: 10/27/2025

Updated: 10/27/2025

Supported Sensors: Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS Score Source: CVE-2025-39992

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 9

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C

Vulnerability Information

CPE: p-cpe:/a:debian:debian_linux:linux, cpe:/o:debian:debian_linux:13.0, cpe:/o:debian:debian_linux:14.0

Required KB Items: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 10/15/2025

Reference Information

CVE: CVE-2025-39992

Detections

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