CVE-2026-53266

netfilter: bridge: make ebt_snat ARP rewrite writable

High Known exploited Linux

Severity: 8.8 / 10; High · CVSS 3.1
Exploit chance (EPSS): 0.93%; Chance of exploitation in the next 30 days. Higher than 60.77% of scored vulnerabilities.
Known exploited: Yes; In CISA's catalog since Sep 18, 2026
Weakness: CWE-787 Out-of-bounds Write
Fix: 7.0.13; Upgrade Kernel to this version or later

Exploited in the wild. Linux Kernel Out-of-Bounds Write Vulnerability (Linux Kernel). 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. Due for U.S. federal agencies by Sep 21, 2026.

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().

Affected versions

Linux

Package	Vulnerable	Fixed in
Kernel	`>= 5.10.0, < 5.10.259` `>= 5.11.0, < 5.15.210` `>= 5.16.0, < 6.1.176` `>= 6.2.0, < 6.6.143` `>= 6.7.0, < 6.12.94` `>= 6.13.0, < 6.18.36` `>= 6.19.0, < 7.0.13`	`5.10.259` `5.15.210` `6.1.176` `6.6.143` `6.12.94` `6.18.36` `7.0.13`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

Kernel Linux → `7.0.13`

Set Kernel to 7.0.13 or later in your manifest.

Severity breakdown

CVSS 3.1 8.8

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

Weakness

CWE-787: Out-of-bounds Write

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

How to prevent it

Requirements: 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.
Architecture and Design: 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 [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.
Operation, Build and Compilation: 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 [REF-1334] discusses canary-based detection in detail.
Implementation: Consider adhering to the following rules when allocating and managing an application's memory: Double check that the buffer is as large as specified. When using functions that accept a number of bytes to copy, such as strncpy(), be aware that if the destination buffer size is equal to the source buffer size, it may not NULL-terminate the string. Check buffer boundaries if accessing the buffer in a loop and make sure there is no danger of writing past the allocated space. If necessary, truncate all input strings to a reasonable length before passing them to the copy and concatenation functions.
Operation, Build and Compilation: Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code. Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking. For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Operation: Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment. For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].
Implementation: Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available.

References

Advisories

Packages

git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Timeline

Jun 25, 2026 Published
Sep 18, 2026 Added to CISA's Known Exploited Vulnerabilities catalog
Sep 21, 2026 Remediation due for U.S. federal agencies
Oct 28, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
CVE-2026-53362 ipv6: account for fraggap on the paged allocation path	High Known exploited	Also affects Kernel
CVE-2026-46300 net: skbuff: preserve shared-frag marker during coalescing	High Known exploited	Also affects Kernel
CVE-2026-31431 crypto: algif_aead - Revert to operating out-of-place	High Known exploited	Also affects Kernel
CVE-2025-39964 crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg	Medium Known exploited	Also affects Kernel
CVE-2025-39682 tls: fix handling of zero-length records on the rx_list	Critical Known exploited	Also affects Kernel
CVE-2025-38352 posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del()	High Known exploited	Also affects Kernel
CVE-2024-53197 ALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devices	High Known exploited	Also affects Kernel
CVE-2024-53150 ALSA: usb-audio: Fix out of bounds reads when finding clock sources	High Known exploited	Also affects Kernel

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