Linux Kernel Missing Initialization of a Variable Vulnerability

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.

Why it matters

• This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, which means it has been observed being exploited in the wild.

Affected

• Vendor: Linux
• Product: Kernel
• Identifier: CVE-2026-46300
• FlawFind severity: high
• Weakness: CWE-456

What to do

• 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.
• U.S. federal remediation deadline: 2026-10-31
• Inventory the affected product, prioritise internet-facing instances, and patch or mitigate immediately.
• Audit your own systems for the same weakness class — FlawFind can test your applications and APIs for it and prove what is exploitable.

Notes

This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; 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 ; https://git.kernel.org/stable/c/3884358a9286b17f389a72b1426fc4547c23c111 ; https://git.kernel.org/stable/c/f84eca5817390257cef78013d0112481c503b4a3 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-46300