CyberSecBulletin
CVE-2026-43011NVD status: Modified

Linux: Double Free

Published Updated By the CyberSecBulletin desk

CVE-2026-43011 is a critical-severity double free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9, 3f5e3005984645bf5bd129c6b13149879580b1fb, f782dd382203b2a8c4552a628431b7de65a19a7b 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 0.59% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to 5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9 or 3f5e3005984645bf5bd129c6b13149879580b1fb or f782dd382203b2a8c4552a628431b7de65a19a7b or 143d4fa68ae9efb83b0c55b12cc7f0d03732a2b1, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.168 or 6.6.134, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 3f5e3005984645bf5bd129c6b13149879580b1fb; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, f782dd382203b2a8c4552a628431b7de65a19a7b; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 143d4fa68ae9efb83b0c55b12cc7f0d03732a2b1; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 524371398d8463ea7e101fce2cbf3915645d1730; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, fa1dbc93530b34fab0da9862426fe9c918c74dc0; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, c87dd137c0dad07cc55f98181ff380b0c23d2878; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, d10a26aa4d072320530e6968ef945c8c575edf61; and 1 more ranges5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9, 3f5e3005984645bf5bd129c6b13149879580b1fb, f782dd382203b2a8c4552a628431b7de65a19a7b, 143d4fa68ae9efb83b0c55b12cc7f0d03732a2b1, 524371398d8463ea7e101fce2cbf3915645d1730, fa1dbc93530b34fab0da9862426fe9c918c74dc0
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.6 and later; V3.1.5 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; V3.1.5 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; V3.1.5 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; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
LinuxLinux Kernel2.6.12.1 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.168; 6.2 up to, but not including, 6.6.134; 6.7 up to, but not including, 6.12.81; 6.13 up to, but not including, 6.18.22; 6.19 up to, but not including, 6.19.12; 2.6.12; and 1 more ranges5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22

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
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
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:N/AC:L/PR:N/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: net/x25: Fix potential double free of skb When alloc_skb fails in x25_queue_rx_frame it calls kfree_skb(skb) at line 48 and returns 1 (error). This error propagates back through the call chain: x25_queue_rx_frame returns 1 | v x25_state3_machine receives the return value 1 and takes the else branch at line 278, setting queued=0 and returning 0 | v x25_process_rx_frame returns queued=0 | v x25_backlog_rcv at line 452 sees queued=0 and calls kfree_skb(skb) again This would free the same skb twice. Looking at x25_backlog_rcv: net/x25/x25_in.c:x25_backlog_rcv() { ... queued = x25_process_rx_frame(sk, skb); ... if (!queued) kfree_skb(skb); }

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: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Double Free vulnerabilities

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