CyberSecBulletin
CVE-2026-46113NVD status: Undergoing Analysis

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-46113 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 9597963a8ca16259d194a1d9950d7bd22a10ab2f, e9d4ea13aa2b6400bb10ec64b370ba3dadcd22f0, 488e386484ec8c0e558be6e156edf34ed9f4d5c8 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.19% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 9597963a8ca16259d194a1d9950d7bd22a10ab2f or e9d4ea13aa2b6400bb10ec64b370ba3dadcd22f0 or 488e386484ec8c0e558be6e156edf34ed9f4d5c8 or 06c19c967b845b63172601fe459667d973b7e6b7, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.175 or 6.6.140 or 6.12.88 or 6.18.30, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, 9597963a8ca16259d194a1d9950d7bd22a10ab2f; 6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, e9d4ea13aa2b6400bb10ec64b370ba3dadcd22f0; 6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, 488e386484ec8c0e558be6e156edf34ed9f4d5c8; 6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, 06c19c967b845b63172601fe459667d973b7e6b7; 6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, 738ec97b1855df6c08fe2369f798fa0b972e556b; 6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, 14d1e55dfd2cf4711bff164a6aaaddb783552134; 6aa8b732ca01c3d7a54e93f4d701b8aabbe60fb7 up to, but not including, 0cb2af2ea66ad8ff195c156ea690f11216285bdf; 2.6.209597963a8ca16259d194a1d9950d7bd22a10ab2f, e9d4ea13aa2b6400bb10ec64b370ba3dadcd22f0, 488e386484ec8c0e558be6e156edf34ed9f4d5c8, 06c19c967b845b63172601fe459667d973b7e6b7, 738ec97b1855df6c08fe2369f798fa0b972e556b, 14d1e55dfd2cf4711bff164a6aaaddb783552134
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
LinuxLinux Kernel2.6.20 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.140; 6.7 up to, but not including, 6.12.88; 6.13 up to, but not including, 6.18.30; 6.19 up to, but not including, 7.0.7; 7.16.1.175, 6.6.140, 6.12.88, 6.18.30, 7.0.7

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Fix shadow paging use-after-free due to unexpected GFN The shadow MMU computes GFNs for direct shadow pages using sp->gfn plus the SPTE index. This assumption breaks for shadow paging if the guest page tables are modified between VM entries (similar to commit aad885e77496, "KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE", 2026-03-27). The flow is as follows: - a PDE is installed for a 2MB mapping, and a page in that area is accessed. KVM creates a kvm_mmu_page consisting of 512 4KB pages; the kvm_mmu_page is marked by FNAME(fetch) as direct-mapped because the guest's mapping is a huge page (and thus contiguous). - the PDE mapping is changed from outside the guest. - the guest accesses another page in the same 2MB area. KVM installs a new leaf SPTE and rmap entry; the SPTE uses the "correct" GFN (i.e. based on the new mapping, as changed in the previous step) but that GFN is outside of the [sp->gfn, sp->gfn + 511] range; therefore the rmap entry cannot be found and removed when the kvm_mmu_page is zapped. - the memslot that covers the first 2MB mapping is deleted, and the kvm_mmu_page for the now-invalid GPA is zapped. However, rmap_remove() only looks at the [sp->gfn, sp->gfn + 511] range established in step 1, and fails to find the rmap entry that was recorded by step 3. - any operation that causes an rmap walk for the same page accessed by step 3 then walks a stale rmap and dereferences a freed kvm_mmu_page. This includes dirty logging or MMU notifier invalidations (e.g., from MADV_DONTNEED). The underlying issue is that KVM's walking of shadow PTEs assumes that if a SPTE is present when KVM wants to install a non-leaf SPTE, then the existing kvm_mmu_page must be for the correct gfn. Because the only way for the gfn to be wrong is if KVM messed up and failed to zap a SPTE... which shouldn't happen, but *actually* only happens in response to a guest write. That bug dates back literally forever, as even the first version of KVM assumes that the GFN matches and walks into the "wrong" shadow page. However, that was only an imprecision until 2032a93d66fa ("KVM: MMU: Don't allocate gfns page for direct mmu pages") came along. Fix it by checking for a target gfn mismatch and zapping the existing SPTE. That way the old SP and rmap entries are gone, KVM installs the rmap in the right location, and everyone is happy.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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