CVE-2026-43011: In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix potential double free of skb

Q: How do I fix CVE-2026-43011?

linux kernel: upgrade to 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12. Exact commands for each OS are on this page.

Q: Is CVE-2026-43011 being exploited?

CVE-2026-43011 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-43011 affect?

CVE-2026-43011 affects linux kernel. Severity is critical (CVSS 9.8). 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

Q: How urgent is CVE-2026-43011?

Priority 59/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

This month

CRITICAL 9.8REMOTEWATCHLISTUPGRADE

CVE-2026-43011 is a critical-severity flaw (CVSS 9.8) affecting linux kernel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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_r

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 52%)
CISA exploited list	No
Weakness	CWE-415
Published	2026-05-01
Last modified	2026-10-19

Publisher (CNA): kernel.org · Vendor: linux

Last updated 2026-10-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-01 15:16 UTCPublished CVE record published
2026-10-19 20:17 UTCUpdated Record last modified

linux linux kernel UPGRADE

Affected: >= 2.6.12.1 and < 5.10.253 · >= 5.11 and < 5.15.203 · >= 5.16 and < 6.1.168 · >= 6.2 and < 6.6.134 · >= 6.7 and < 6.12.81 · >= 6.13 and < 6.18.22 · >= 6.19 and < 6.19.12 · 2.6.12

Fixed in: 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

Fedora 46 · fzssh · FIXED · 1.4.0-2.fc46 · FEDORA-2026-8004fcd067 · source

sudo dnf upgrade --advisory=FEDORA-2026-8004fcd067

Ubuntu 24.04 · linux · FIXED · 6.8.0-134.134

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.8.0-134.134" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 20.04 · linux · FIXED · 5.4.0-233.253

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.4.0-233.253" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · linux · FIXED · 5.15.0-185.195

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.15.0-185.195" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.10 · linux · FIXED · 6.17.0-40.40

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.17.0-40.40" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 20.04 · linux-hwe-5.15 · FIXED · 5.15.0-185.195~20.04.1

sudo apt update && sudo apt install --only-upgrade linux-hwe-5.15 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux-hwe-5.15)" ge "5.15.0-185.195~20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · linux · FIXED · 6.1.170-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.1.170-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · linux · FIXED · 6.12.85-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.12.85-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · kernel · NOT AFFECTED

RHEL 6 · kernel · NOT AFFECTED

RHEL 7 · kernel · NOT AFFECTED

RHEL 7 · kernel-rt · NOT AFFECTED

RHEL 8 · kernel · NOT AFFECTED

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: cert-portal.siemens.com/productcert/html/ssa-019113.html
Write-up: cert-portal.siemens.com/productcert/html/ssa-082556.html
Write-up: cert-portal.siemens.com/productcert/html/ssa-457936.html

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-43011?

linux kernel: upgrade to 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12. Exact commands for each OS are on this page.

Is CVE-2026-43011 being exploited?

CVE-2026-43011 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-43011 affect?

CVE-2026-43011 affects linux kernel. Severity is critical (CVSS 9.8). 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

How urgent is CVE-2026-43011?

Priority 59/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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