Linux · Kernel
CVE-2026-53266
netfilter: bridge: make ebt_snat ARP rewrite writable
What it is
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().
CISA: Linux Kernel contains an out-of-bounds write vulnerability in the ebtables SNAT target which allows an ARP sender hardware address rewrite to write directly into a nonlinear socket-buffer fragment backed by a splice-imported file page. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.
What to do
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.
Deadline for US federal agencies: September 21, 2026
- Added to the CISA list
- September 18, 2026
- Published
- June 25, 2026
- Severity
- High 8.8 CVSS 3.1
- Chance of attacks in the next 30 days (EPSS)
- 0.9% in the top 39.4% of all known vulnerabilities
- Weakness
- CWE-787
- More details
- NVD · CVE.org · CISA
All references (8)
- https://git.kernel.org/stable/c/bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87
- https://git.kernel.org/stable/c/76280b78cc9f23bdc6438e10ad6dff148ef8375b
- https://git.kernel.org/stable/c/b7e91939ba9be805a62a257fa4e227dffbb88fa0
- https://git.kernel.org/stable/c/afd64b59c3de9bbbdd3759e834fdc55cda716e0b
- https://git.kernel.org/stable/c/153ea96c806aea395daba907a4f88480b6ad5093
- https://git.kernel.org/stable/c/b18675263db1147c8e1cab625400c13a0d87bd2d
- https://git.kernel.org/stable/c/c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5
- https://git.kernel.org/stable/c/67ba971ae02514d85818fe0c32549ab4bfa3bf49
More exploited flaws from Linux
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Sep 18, 2026 | Improper Check for Unusual or Exceptional Conditions | Kernel | Critical 9.8 | 3.3% |
| Sep 18, 2026 | Race Condition | Kernel | High 7.8 | 1.6% |
| Aug 27, 2026 | Unspecified | Kernel | High 7.8 | 0.7% |
| Aug 26, 2026 | Out-of-Bounds Write | Kernel | High 7.8 | 8.9% |
| Jun 2, 2026 | Improper Authentication | Kernel | High 7.8 | 5.5% |
| May 1, 2026 | Incorrect Resource Transfer Between Spheres | Kernel | High 7.8 | 98% |
| Jan 26, 2026 | Integer Overflow | Kernel | High 7.8 | 15% |
| Oct 6, 2025 | Heap Out-of-Bounds Write | Kernel | High 8.3 | 79% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.