~/exploited / cve-2026-46300

CVE-2026-46300: Linux Kernel

According to CISA this vulnerability is already used in attacks (added on 28 October 2026).

Key facts

Description (CISA)

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.

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.

What admins should do now

1. Affected? Check whether Linux Kernel is in use and which version runs (package manager, admin UI, --version).
2. Apply the vendor patch or workaround as soon as it exists. If that is not possible right away: restrict outside access (firewall, VPN, reverse proxy).
3. Review logs back to 28 October 2026: unusual logins, new files, unexpected processes, outbound connections.
4. If you suspect a compromise: isolate the system, rotate credentials, check the last backup from before the incident.

The deadline applies to US federal agencies. It is still a useful yardstick for everyone: when a flaw is attacked in the wild, waiting is not an option.

Sources

• CISA KEV Catalog
• NVD CVE-2026-46300
• git.kernel.org/stable/c/3599e6b3cc1ada96883d496a50a210d3afbb6987
• git.kernel.org/stable/c/2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c
• git.kernel.org/stable/c/9d3e5fd19fe1063bf607219e8562fbd567b8e8d5
• git.kernel.org/stable/c/78bf6b6bb19541d19fbda6242e7cfe2c682763c0
• git.kernel.org/stable/c/760e1addc27ba1a7beb4a0a7e8b3e9ec49e7a34e
• git.kernel.org/stable/c/3bd9e113d50034db99d7ef69fd8e5242d15e414a

Data: CISA Known Exploited Vulnerabilities Catalog, as of 30 October 2026. No guarantee — always check the vendor's advisory.

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