CVE-2026-46300: in the CISA KEV catalogue
Linux Kernel Missing Initialization of a Variable Vulnerability. CISA added CVE-2026-46300 to the Known Exploited Vulnerabilities catalogue on 2026-10-28 with a default due date of 2026-10-31. Known ransomware campaign use: Unknown. Forensic triage flag: Yes.
Linux Kernel contains a missing initialization of a variable vulnerability that could allow for unintended modification of page-cache-backed data via failure to preserve the shared-fragment marker during socket buffer coalescing, causing ESP input processing to decrypt shared fragments in place. This vulnerability can be chained with CVE-2026-109618 and CVE-2026-109619 to implant PHP webshells and run commands as root. (CISA description)
- Vendor / product
- Linux Kernel
- CWE
- CWE-456
- 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
- 16%, percentile 96 (scored 2026-11-03)
EPSS puts about 16 in 100 odds (16%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 96% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
- https://git.kernel.org/stable/c/3599e6b3cc1ada96883d496a50a210d3afbb6987
- https://git.kernel.org/stable/c/2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c
- https://git.kernel.org/stable/c/9d3e5fd19fe1063bf607219e8562fbd567b8e8d5
- https://git.kernel.org/stable/c/78bf6b6bb19541d19fbda6242e7cfe2c682763c0
- https://git.kernel.org/stable/c/760e1addc27ba1a7beb4a0a7e8b3e9ec49e7a34e
- https://git.kernel.org/stable/c/3bd9e113d50034db99d7ef69fd8e5242d15e414a
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-2026-46300 in the CISA KEV catalogue?
Yes. CISA added CVE-2026-46300 (Linux Kernel Missing Initialization of a Variable Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-10-28. CISA's default due date for it is 2026-10-31.
Is CVE-2026-46300 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2026-46300. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2026-46300?
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-2026-46300