CVE-2026-53266: in the CISA KEV catalogue
Linux Kernel Out-of-Bounds Write Vulnerability. CISA added CVE-2026-53266 to the Known Exploited Vulnerabilities catalogue on 2026-09-18 with a default due date of 2026-09-21. Known ransomware campaign use: Unknown. Forensic triage flag: Yes.
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. (CISA description)
- Vendor / product
- Linux Kernel
- CWE
- CWE-787
- CISA 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.
- EPSS
- 0.93%, percentile 60 (scored 2026-11-03)
EPSS puts about 9.3 in 1,000 odds (0.93%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 60% of scored CVEs. Most CVEs score under 1%, so a high percentile can sit on a small probability: read the percentage first.
Vendor and reference links (from CISA)
- 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
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2026-53266 in the CISA KEV catalogue?
Yes. CISA added CVE-2026-53266 (Linux Kernel Out-of-Bounds Write Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-09-18. CISA's default due date for it is 2026-09-21.
Is CVE-2026-53266 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2026-53266. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2026-53266?
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.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2026-53266