CVE-2026-53266: Linux Kernel Out-of-Bounds Write Vulnerability

Q: How do I fix CVE-2026-53266?

linux kernel: upgrade to 5.5, 5.9, 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13. Exact commands for each OS are on this page.

Q: Is CVE-2026-53266 being exploited?

Yes. CVE-2026-53266 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

Q: What does CVE-2026-53266 affect?

CVE-2026-53266 affects linux kernel. Severity is high (CVSS 8.8). In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: make ebt_snat ARP rewrite writable The ebtables SNAT target keeps the Ethernet source address rewrite behind skb_ensure_writable(skb, 0). This is inte

Q: How urgent is CVE-2026-53266?

Priority 75/100. High severity; Exploited in the wild (CISA KEV); On your watchlist

Patch now

HIGH 8.8EXPLOITEDWATCHLISTUPGRADE

CVE-2026-53266 is a high-severity flaw (CVSS 8.8) affecting linux kernel, reported as exploited in the wild. 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: netfilter: bridge: make ebt_snat ARP rewrite writable The ebtables SNAT target keeps the Ethernet source address rewrite behind skb_ensure_writable(skb, 0). This is intentional: at the bridge ebtables hooks the Ethernet header is addressed through skb_mac_header()/eth_hdr(), while skb->data points at the Ethernet payload. Asking skb_ensure_writable() for ETH_HLEN bytes would

Why this priority

High severity
Exploited in the wild (CISA KEV)
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.8% (top 43%)
CISA exploited list	Yes, fix due 2026-09-21
Weakness	CWE-787
Published	2026-06-25
Last modified	2026-09-19

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

Last updated 2026-09-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-25 09:16 UTCPublished CVE record published
2026-09-18Exploited Added to the CISA Known Exploited Vulnerabilities list
2026-09-19 04:17 UTCUpdated Record last modified
2026-09-21Deadline CISA due date for US federal agencies to patch

linux linux kernel UPGRADE

Affected: >= 5.4.73 and < 5.5 · >= 5.8.17 and < 5.9 · >= 5.9.2 and < 5.10.259 · >= 5.11 and < 5.15.210 · >= 5.16 and < 6.1.176 · >= 6.2 and < 6.6.143 · >= 6.7 and < 6.12.94 · >= 6.13 and < 6.18.36

Fixed in: 5.5, 5.9, 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13

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 · python-streamlink · FIXED · 8.6.2-1.fc46 · FEDORA-2026-a56fcfdc08 · source

sudo dnf upgrade --advisory=FEDORA-2026-a56fcfdc08

Fedora ELN · valgrind · FIXED · 3.28.0-1.eln159 · FEDORA-2026-c593ef1d15 · source

sudo dnf upgrade --advisory=FEDORA-2026-c593ef1d15

Ubuntu 20.04 · linux · NO FIX YET

Ubuntu 22.04 · linux · FIXED · 5.15.0-198.208

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.15.0-198.208" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · linux · FIXED · 6.8.0-146.146

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.8.0-146.146" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 20.04 · linux-hwe-5.15 · FIXED · 5.15.0-198.208~20.04.1

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 "5.15.0-198.208~20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · linux-hwe-6.8 · NO FIX YET

Debian 12 · linux · FIXED · 6.1.176-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.1.176-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · linux · FIXED · 6.12.94-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.12.94-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · kernel · FIXED · kernel-6.12.0-211.59.1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:71233 rpm -q kernel

RHEL 10.0 Extended Update Support · kernel · FIXED · kernel-6.12.0-55.106.1.el10_0

sudo dnf upgrade --advisory=RHSA-2026:71326 rpm -q kernel

RHEL 6 Extended Lifecycle Support - EXTENSION · kernel · FIXED · kernel-2.6.32-754.64.1.el6

sudo dnf upgrade --advisory=RHSA-2026:73732 rpm -q kernel

RHEL 7 Extended Lifecycle Support · kernel-rt · FIXED · kernel-rt-3.10.0-1160.164.1.rt56.1316.el7

sudo dnf upgrade --advisory=RHSA-2026:71657 rpm -q kernel-rt

RHEL 7 Extended Lifecycle Support · kernel · FIXED · kernel-3.10.0-1160.164.1.el7

sudo dnf upgrade --advisory=RHSA-2026:71687 rpm -q kernel

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1968 · source

sudo dnf update --advisory=ALAS2023-2026-1968

Public exploits and detection

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

GitHub PoC: suominen/CVE-2026-53266 (0 stars)

Verify at the official source NVD · CVE Program · CISA KEV catalog · 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-2026-53266?

linux kernel: upgrade to 5.5, 5.9, 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13. Exact commands for each OS are on this page.

Is CVE-2026-53266 being exploited?

Yes. CVE-2026-53266 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2026-53266 affect?

CVE-2026-53266 affects linux kernel. Severity is high (CVSS 8.8). In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: make ebt_snat ARP rewrite writable The ebtables SNAT target keeps the Ethernet source address rewrite behind skb_ensure_writable(skb, 0). This is inte

How urgent is CVE-2026-53266?

Priority 75/100. High severity; Exploited in the wild (CISA KEV); On your watchlist

Software pages

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References

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