CVE-2026-53266 — Linux Kernel Out-of-Bounds Write Vulnerability
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().
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Confirmed exploitation (CISA KEV)+35
- Public exploit/PoC (github)+6
- EPSS 0.8% (30-day exploitation probability)+8
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
CISA required action CISA
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.
US federal deadline: Sep 21, 2026 — passed 24 day(s) ago
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87version 5.10≥ 5.9.2 and < 5.10≥ 5.8.17 and < 5.9≥ 5.4.73 and < 5.5version b7d23c2c87584eb429f115c078ed511be8b18e29version 51ba2945a8ef65ae437c8f9ba05f0343aa82ae5bversion 2f3839075a5f8dcf116c1abe35b36b018ac62445 and 7 more≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < 67ba971ae02514d85818fe0c32549ab4bfa3bf49≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < b18675263db1147c8e1cab625400c13a0d87bd2d≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < 153ea96c806aea395daba907a4f88480b6ad5093≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < afd64b59c3de9bbbdd3759e834fdc55cda716e0b≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < b7e91939ba9be805a62a257fa4e227dffbb88fa0≥ 63137bc5882a1882c553d389fdeeeace86ee1741 and < 76280b78cc9f23bdc6438e10ad6dff148ef8375b |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
≥ 5.4.73 and < 5.5version 7.1-rc6version 7.1-rc5version 7.1-rc4version 7.1-rc3version 7.1-rc2version 7.1-rc1≥ 6.19 and < 7.0.13 and 7 more≥ 6.13 and < 6.18.36≥ 6.7 and < 6.12.94≥ 6.2 and < 6.6.143≥ 5.16 and < 6.1.176≥ 5.11 and < 5.15.210≥ 5.9.2 and < 5.10.259≥ 5.8.17 and < 5.9 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.8 | CVSS 3.1 | High | 2.0 | 6.0 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 8.8 | CVSS 3.1 | High | — | — | GitHub, Inc. via GitHub Security Advisories |
| 8.8 | CVSS 3.1 | High | — | — | Linux via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
CISA KEV details CISA
CISA lists a CVE once it has evidence of exploitation against real targets.
CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.
Public exploits, PoCs and detection templates
Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.
Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.
EPSS over time FIRST
Oct 12, 2026 → Oct 14, 2026 · 3 reading(s) · max 0.83%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
- Hunt retroactively in logs from before Sep 18, 2026 (KEV listing): exploitation may have started earlier.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · linux/linux kernel
- CVSS changed · 8.8
- Source status changed · → Analyzed
- Added to CISA KEV (detected)
- Record created in this database
- Added to CISA KEV catalog
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 13, 2026 – Oct 13, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
11 on the record
- git.kernel.org/stable/c/bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87
- git.kernel.org/stable/c/b7e91939ba9be805a62a257fa4e227dffbb88fa0
- git.kernel.org/stable/c/67ba971ae02514d85818fe0c32549ab4bfa3bf49
- git.kernel.org/stable/c/afd64b59c3de9bbbdd3759e834fdc55cda716e0b
- git.kernel.org/stable/c/c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5
- git.kernel.org/stable/c/153ea96c806aea395daba907a4f88480b6ad5093
- git.kernel.org/stable/c/76280b78cc9f23bdc6438e10ad6dff148ef8375b
- git.kernel.org/stable/c/b18675263db1147c8e1cab625400c13a0d87bd2d
- www.cisa.gov/known-exploited-vulnerabilities-catalog
- nvd.nist.gov/vuln/detail/CVE-2026-53266
- github.com/advisories/GHSA-xmhg-rr34-2chj
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 10h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 10h
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-53266 is "Linux Kernel Out-of-Bounds Write Vulnerability", rated High. It affects Linux (Linux); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 8.8 describes technical severity. EPSS 0.83% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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