CyberSecBulletin
CVE-2026-53266Exploited in the wildNVD status: Analyzed

Linux Kernel Out-of-Bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-53266 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 8.8 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 bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87, 76280b78cc9f23bdc6438e10ad6dff148ef8375b, b7e91939ba9be805a62a257fa4e227dffbb88fa0 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on September 18, 2026, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Linux to bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87 or 76280b78cc9f23bdc6438e10ad6dff148ef8375b or b7e91939ba9be805a62a257fa4e227dffbb88fa0 or afd64b59c3de9bbbdd3759e834fdc55cda716e0b, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.5 or 5.9 or 5.10.259 or 5.15.210, whichever matches your release line, or a later version.
  3. CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, 76280b78cc9f23bdc6438e10ad6dff148ef8375b; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, b7e91939ba9be805a62a257fa4e227dffbb88fa0; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, afd64b59c3de9bbbdd3759e834fdc55cda716e0b; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, 153ea96c806aea395daba907a4f88480b6ad5093; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, b18675263db1147c8e1cab625400c13a0d87bd2d; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5; 63137bc5882a1882c553d389fdeeeace86ee1741 up to, but not including, 67ba971ae02514d85818fe0c32549ab4bfa3bf49; and 7 more rangesbf84ad7c7a9ede46e31afaa41a1ba06a159e8c87, 76280b78cc9f23bdc6438e10ad6dff148ef8375b, b7e91939ba9be805a62a257fa4e227dffbb88fa0, afd64b59c3de9bbbdd3759e834fdc55cda716e0b, 153ea96c806aea395daba907a4f88480b6ad5093, b18675263db1147c8e1cab625400c13a0d87bd2d
LinuxLinux Kernel5.4.73 up to, but not including, 5.5; 5.8.17 up to, but not including, 5.9; 5.9.2 up to, but not including, 5.10.259; 5.11 up to, but not including, 5.15.210; 5.16 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.94; 6.13 up to, but not including, 6.18.36; and 2 more ranges5.5, 5.9, 5.10.259, 5.15.210, 6.1.176, 6.6.143

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
ChangedThe attack can reach beyond the vulnerable component into other systems.
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:C/C:H/I:H/A:H. Scored by CNA.

Official description

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 check the payload, not the Ethernet header, and would reintroduce the small packet regression fixed by commit 63137bc5882a. However, the optional ARP sender hardware address rewrite is different. It writes through skb_store_bits() at an offset relative to skb->data: skb_store_bits(skb, sizeof(struct arphdr), info->mac, ETH_ALEN) skb_header_pointer() only safely reads the ARP header; it does not make the later sender hardware address range writable. If that range is still held in a nonlinear skb fragment backed by a splice-imported file page, skb_store_bits() maps the frag page and copies the new MAC address directly into it. Ensure the ARP SHA range is writable before reading the ARP header and before calling skb_store_bits().

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

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Record last changed materially (score, affected products, status or references).
  5. Deadline for US federal agencies to remediate, set by CISA.

References

Third-party and government advisories

Recent Out-of-bounds Write vulnerabilities

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