---
title: "CVE-2026-46300: Linux Kernel Missing Initialization of a Variable Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-46300/
description: "CVE-2026-46300 (Linux Kernel): Exploited in the wild (CISA KEV). In the Linux kernel, the following vulnerability has been resolved: net: skbuff: preserve…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-05-23
date_modified: 2026-10-29
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-46300"
kev: true
cvss: 7.8
epss: 0.1613
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-46300: Linux Kernel Missing Initialization of a Variable Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Linux Kernel. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-10-28, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-10-31 ; treat that as the outer limit, not the target.
- EPSS 16.1% , percentile 97: FIRST’s model estimates a 16.1% chance of exploitation activity in the next 30 days, higher than 97% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
- Editorial verdict: Act now. Fragnesia: Exploited Linux Kernel Root Bug CVE-2026-46300 — Any Linux host that runs untrusted or internet-facing code should be on a kernel with the May 2026 fix today; attackers are now using this public, race-free root exploit right after a web foothold.

## What it is

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: preserve shared-frag marker during coalescing skbtrycoalesce() can attach paged frags from @from to @to. If @from has SKBFLSHAREDFRAG set, the resulting @to skb can contain the same externally-owned or page-cache-backed frags, but the shared-frag marker is currently lost. That breaks the invariant relied on by later in-place writers. In particular, ESP input checks skbhassharedfrag() before deciding whether an uncloned nonlinear skb can skip skbcowdata(). If TCP receive coalescing has moved shared frags into an unmarked skb, ESP can see skbhassharedfrag() as false and decrypt in place over page-cache backed frags. Propagate SKBFLSHAREDFRAG when skbtrycoalesce() transfers paged frags. The tailroom copy path does not need the marker because it copies bytes into @to's linear data rather than transferring frag descriptors.

## Affected products (CVE record)

- Linux Linux: cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 3599e6b3cc1ada96883d496a50a210d3afbb6987, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 9d3e5fd19fe1063bf607219e8562fbd567b8e8d5, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 78bf6b6bb19541d19fbda6242e7cfe2c682763c0, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 760e1addc27ba1a7beb4a0a7e8b3e9ec49e7a34e, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 3bd9e113d50034db99d7ef69fd8e5242d15e414a, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < 3884358a9286b17f389a72b1426fc4547c23c111, cef401de7be8c4e155c6746bfccf721a4fa5fab9 < f84eca5817390257cef78013d0112481c503b4a3
- Linux Linux: 3.9

## Severity

- Linux CVSS 3.1: 7.8 `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`
- redhat-SADP CVSS 3.1: 7.8 `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: added 2026-10-28; federal due date 2026-10-31. Known ransomware use: Unknown.
- 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.
- CISA SSVC assessment: exploitation active , automatable no , technical impact total .
- FIRST EPSS (model of 2026-11-05): 16.13% probability of exploitation activity in the next 30 days; percentile 97.

## Sources

- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19540)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:33486)
- [access.redhat.com](https://access.redhat.com/errata/RHBA-2026:20032)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:21695)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:21690)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:28887)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23233)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20087)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:25044)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:34098)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:21656)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23245)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:21702)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23240)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20299)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19569)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19705)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20593)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20054)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20129)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19568)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19666)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23470)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20130)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:20051)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19521)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23471)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23469)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:24814)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:23468)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19664)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19711)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:19875)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/3599e6b3cc1ada96883d496a50a210d3afbb6987)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/9d3e5fd19fe1063bf607219e8562fbd567b8e8d5)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/78bf6b6bb19541d19fbda6242e7cfe2c682763c0)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/760e1addc27ba1a7beb4a0a7e8b3e9ec49e7a34e)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/3bd9e113d50034db99d7ef69fd8e5242d15e414a)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/3884358a9286b17f389a72b1426fc4547c23c111)
- [Listed in CISA KEV notes (git.kernel.org)](https://git.kernel.org/stable/c/f84eca5817390257cef78013d0112481c503b4a3)
- [CVE.org record CVE-2026-46300](https://www.cve.org/CVERecord?id=CVE-2026-46300)
- [NVD entry CVE-2026-46300](https://nvd.nist.gov/vuln/detail/CVE-2026-46300)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-46300)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/05/13/5)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/05/21/11)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/05/21/12)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/05/21/13)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2026-46300)
- [RHBZ#2477015](https://bugzilla.redhat.com/show_bug.cgi?id=2477015)
- [security.access.redhat.com](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46300.json)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/html/ssa-082556.html)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

---
Source page: https://erroneo.us/security/cve/CVE-2026-46300/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt