CVE-2026-53266
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().
do firstUpgrade to a fixed release: < 5.10, >= 5.10.259 and <= 5.10.*, >= 5.15.210 and <= 5.15.*, >= 6.1.176 and <= 6.1.* (+5 more below).
Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.
Also consider: patch
Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2026-53266 being exploited?
Yes. CVE-2026-53266 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2026-53266?
CVE-2026-53266 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-53266?
Yes. A fix has been recorded for CVE-2026-53266. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-53266 affect?
CVE-2026-53266 affects linux:linux_kernel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < 76280b78cc9f23bdc6438e10ad6dff148ef8375b
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < b7e91939ba9be805a62a257fa4e227dffbb88fa0
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < afd64b59c3de9bbbdd3759e834fdc55cda716e0b
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < 153ea96c806aea395daba907a4f88480b6ad5093
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < b18675263db1147c8e1cab625400c13a0d87bd2d
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5
- affected>= 63137bc5882a1882c553d389fdeeeace86ee1741 and < 67ba971ae02514d85818fe0c32549ab4bfa3bf49
- affected2f3839075a5f8dcf116c1abe35b36b018ac62445
- affected51ba2945a8ef65ae437c8f9ba05f0343aa82ae5b
- affectedb7d23c2c87584eb429f115c078ed511be8b18e29
- affected>= 5.4.73 and < 5.5
- affected>= 5.8.17 and < 5.9
- affected>= 5.9.2 and < 5.10
- affected5.10
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
public exploits
Unvetted proof-of-concept code on GitHub: 1 GitHub proof of concept
- suominen/CVE-2026-53266 · 0 ★
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 18 Sept 2026 (SSVC 2.0.3).
timeline
- 25 Jun 2026Published
- 18 Sept 2026Added to CISA KEV (exploited in the wild) · 85 days (about 3 months) later
- 18 Sept 2026CISA SSVC assessment: exploitation active · same day later
- 19 Sept 2026CVE record last updated · 1 day later
- 20 Sept 2026First proof-of-concept repository on GitHub (unvetted) · 1 day later
- 21 Sept 2026CISA remediation due date (US federal agencies) · 1 day later
- 2 Nov 2026Analysed by vulneraibility.com · 43 days later
- Linkgit.kernel.org /stable/c/bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87
- Linkgit.kernel.org /stable/c/76280b78cc9f23bdc6438e10ad6dff148ef8375b
- Linkgit.kernel.org /stable/c/b7e91939ba9be805a62a257fa4e227dffbb88fa0
- Linkgit.kernel.org /stable/c/afd64b59c3de9bbbdd3759e834fdc55cda716e0b
- Linkgit.kernel.org /stable/c/153ea96c806aea395daba907a4f88480b6ad5093
- Linkgit.kernel.org /stable/c/b18675263db1147c8e1cab625400c13a0d87bd2d
- Linkgit.kernel.org /stable/c/c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5
- Linkgit.kernel.org /stable/c/67ba971ae02514d85818fe0c32549ab4bfa3bf49
Show 1 more
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-53266
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.