CyberSecBulletin
CVE-2026-43303NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-43303 is a high-severity use after 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 e7790ab165713b79b1617ce659742ceb3a859d05, 3edb8ebbf79b9016040e8f3421d723ae3d542b32, f9719e32a67b4b00b3c9b133e8b5ffa72a26b67b 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 0.17% 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 e7790ab165713b79b1617ce659742ceb3a859d05 or 3edb8ebbf79b9016040e8f3421d723ae3d542b32 or f9719e32a67b4b00b3c9b133e8b5ffa72a26b67b or 23b82b7a26182ad840ae67d390d7ec9771e8c00f, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.18.16 or 6.19.6, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux3b8000ae185cb068adbda5f966a3835053c85fd4 up to, but not including, e7790ab165713b79b1617ce659742ceb3a859d05; 3b8000ae185cb068adbda5f966a3835053c85fd4 up to, but not including, 3edb8ebbf79b9016040e8f3421d723ae3d542b32; 3b8000ae185cb068adbda5f966a3835053c85fd4 up to, but not including, f9719e32a67b4b00b3c9b133e8b5ffa72a26b67b; 3b8000ae185cb068adbda5f966a3835053c85fd4 up to, but not including, 23b82b7a26182ad840ae67d390d7ec9771e8c00f; 3b8000ae185cb068adbda5f966a3835053c85fd4 up to, but not including, d757c793853ec5483eb41ec2942c300b8fa720fb; 3b8000ae185cb068adbda5f966a3835053c85fd4 up to, but not including, ac1ea219590c09572ed5992dc233bbf7bb70fef9; 5.18e7790ab165713b79b1617ce659742ceb3a859d05, 3edb8ebbf79b9016040e8f3421d723ae3d542b32, f9719e32a67b4b00b3c9b133e8b5ffa72a26b67b, 23b82b7a26182ad840ae67d390d7ec9771e8c00f, d757c793853ec5483eb41ec2942c300b8fa720fb, ac1ea219590c09572ed5992dc233bbf7bb70fef9
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)V3.1.6 and later; V3.1.7 and laterNot stated
LinuxLinux Kernel5.18.1 up to, but not including, 6.18.16; 6.19 up to, but not including, 6.19.6; 5.186.18.16, 6.19.6

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 CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: mm/page_alloc: clear page->private in free_pages_prepare() Several subsystems (slub, shmem, ttm, etc.) use page->private but don't clear it before freeing pages. When these pages are later allocated as high-order pages and split via split_page(), tail pages retain stale page->private values. This causes a use-after-free in the swap subsystem. The swap code uses page->private to track swap count continuations, assuming freshly allocated pages have page->private == 0. When stale values are present, swap_count_continued() incorrectly assumes the continuation list is valid and iterates over uninitialized page->lru containing LIST_POISON values, causing a crash: KASAN: maybe wild-memory-access in range [0xdead000000000100-0xdead000000000107] RIP: 0010:__do_sys_swapoff+0x1151/0x1860 Fix this by clearing page->private in free_pages_prepare(), ensuring all freed pages have clean state regardless of previous use.

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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