CyberSecBulletin
CVE-2026-31787NVD status: Analyzed

Linux: Double Free

Published Updated By the CyberSecBulletin desk

CVE-2026-31787 is a high-severity double free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 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 dbf862ce9f009128ab86b234d91413a3e450beb4, 2b985d3a024b9e8c24e21671b34e855569763808, 1576ff3869cbd3620717195f971c85b7d7fd62b5 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 0.18% 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 dbf862ce9f009128ab86b234d91413a3e450beb4 or 2b985d3a024b9e8c24e21671b34e855569763808 or 1576ff3869cbd3620717195f971c85b7d7fd62b5 or 402d84ad9e89bd4cbfd07ca8598532b7021daf95, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.254 or 5.15.204 or 6.1.170 or 6.6.137, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxd71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, dbf862ce9f009128ab86b234d91413a3e450beb4; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 2b985d3a024b9e8c24e21671b34e855569763808; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 1576ff3869cbd3620717195f971c85b7d7fd62b5; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 402d84ad9e89bd4cbfd07ca8598532b7021daf95; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 2894a351fe2ea8684919d36df3188b9a35e3926f; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 446ee446d9ae66f36e95c3c90bbcc4e56b94cde0; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 71bf829800758a6e3889096e4754ef47ba7fc850; d71f513985c22f1050295d1a7e4327cf9fb060da up to, but not including, 24daca4fc07f3ff8cd0e3f629cd982187f48436a; and 1 more rangesdbf862ce9f009128ab86b234d91413a3e450beb4, 2b985d3a024b9e8c24e21671b34e855569763808, 1576ff3869cbd3620717195f971c85b7d7fd62b5, 402d84ad9e89bd4cbfd07ca8598532b7021daf95, 2894a351fe2ea8684919d36df3188b9a35e3926f, 446ee446d9ae66f36e95c3c90bbcc4e56b94cde0
LinuxLinux Kernel3.8 up to, but not including, 5.10.254; 5.11 up to, but not including, 5.15.204; 5.16 up to, but not including, 6.1.170; 6.2 up to, but not including, 6.6.137; 6.7 up to, but not including, 6.12.85; 6.13 up to, but not including, 6.18.26; 6.19 up to, but not including, 7.0.3; 7.15.10.254, 5.15.204, 6.1.170, 6.6.137, 6.12.85, 6.18.26

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
UnchangedImpact stays within the vulnerable component.
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:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: xen/privcmd: fix double free via VMA splitting privcmd_vm_ops defines .close (privcmd_close), but neither .may_split nor .open. When userspace does a partial munmap() on a privcmd mapping, the kernel splits the VMA via __split_vma(). Since may_split is NULL, the split is allowed. vm_area_dup() copies vm_private_data (a pages array allocated in alloc_empty_pages()) into the new VMA without any fixup, because there is no .open callback. Both VMAs now point to the same pages array. When the unmapped portion is closed, privcmd_close() calls: - xen_unmap_domain_gfn_range() - xen_free_unpopulated_pages() - kvfree(pages) The surviving VMA still holds the dangling pointer. When it is later destroyed, the same sequence runs again, which leads to a double free. Fix this issue by adding a .may_split callback denying the VMA split. This is XSA-487 / CVE-2026-31787

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

The underlying weakness: Double Free

The product calls free() twice on the same memory address.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
  • Use a static analysis tool to find double free instances.

More Double Free vulnerabilities (CWE-415)

Timeline

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

References

Third-party and government advisories

Recent Double Free vulnerabilities

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