Linux Kernel up to 6.12.50/6.16.10/6.17.0 mm unuse_mm null pointer dereference

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4.6$0-$5k0.00

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 6.12.50/6.16.10/6.17.0. This affects the function unuse_mm of the component mm. This manipulation causes null pointer dereference. This vulnerability appears as CVE-2025-39992. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.12.50/6.16.10/6.17.0. It has been declared as critical. Affected by this vulnerability is the function unuse_mm of the component mm. The manipulation with an unknown input leads to a null pointer dereference vulnerability. The CWE definition for the vulnerability is CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. As an impact it is known to affect availability. The summary by CVE is:

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

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2025-39992 since 04/16/2025. The exploitation appears to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 277016 (openSUSE 16 Security Update : kernel (openSUSE-SU-2025-20091-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.12.51, 6.16.11, 6.17.1 or 6.18-rc1 eliminates this vulnerability. Applying the patch 4e5f060d7347466f77aaff1c0d5a6c4f1fb217ac/9cddad3b26dac830407d2d3c0de5205ff6d6dda0/e4e99d69b8b8295c501b2eef89e13306b738b667/1367da7eb875d01102d2ed18654b24d261ff5393 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (277016) and CERT Bund (WID-SEC-2025-2298). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel
  • IBM QRadar SIEM
  • Dell NetWorker

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.8
VulDB Meta Temp Score: 4.6

VulDB Base Score: 4.8
VulDB Temp Score: 4.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Null pointer dereference
CWE: CWE-476 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 277016
Nessus Name: openSUSE 16 Security Update : kernel (openSUSE-SU-2025-20091-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.12.51/6.16.11/6.17.1/6.18-rc1
Patch: 4e5f060d7347466f77aaff1c0d5a6c4f1fb217ac/9cddad3b26dac830407d2d3c0de5205ff6d6dda0/e4e99d69b8b8295c501b2eef89e13306b738b667/1367da7eb875d01102d2ed18654b24d261ff5393

Timelineinfo

04/16/2025 CVE reserved
10/15/2025 +182 days Advisory disclosed
10/15/2025 +0 days VulDB entry created
02/08/2026 +116 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-39992 (🔒)
GCVE (CVE): GCVE-0-2025-39992
GCVE (VulDB): GCVE-100-328633
CERT Bund: WID-SEC-2025-2298 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 10/15/2025 12:06
Updated: 02/08/2026 20:15
Changes: 10/15/2025 12:06 (59), 11/03/2025 18:47 (7), 11/22/2025 18:08 (1), 12/03/2025 11:11 (2), 12/21/2025 09:10 (1), 02/08/2026 20:15 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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