CVE-2026-46300

High

Linux Kernel Missing Initialization of a Variable Vulnerability

7.8 CVSS v3.1

Published: May 23, 2026
Updated: Oct 28, 2026
Vendor: Linux
Affected versions: See affected products
Weakness: CWE-787, CWE-456, CWE-123

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: skbuff: preserve shared-frag marker during coalescing

skb_try_coalesce() can attach paged frags from @from to @to. If @from
has SKBFL_SHARED_FRAG 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 skb_has_shared_frag() before deciding
whether an uncloned nonlinear skb can skip skb_cow_data(). If TCP
receive coalescing has moved shared frags into an unmarked skb, ESP can
see skb_has_shared_frag() as false and decrypt in place over page-cache
backed frags.

Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() 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.

Severity

High (7.8)

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Linux Linux Kernel >= 3.9, <= 5.10.257
Linux Linux Kernel >= 5.11, < 5.15.208
Linux Linux Kernel >= 5.16, < 6.1.174
Linux Linux Kernel >= 6.2, < 6.6.141
Linux Linux Kernel >= 6.7, < 6.12.91
Linux Linux Kernel >= 6.13, < 6.18.33
Linux Linux Kernel >= 6.19, < 7.0.10
Linux Linux Kernel 7.1

Exploitation status

Actively exploited

Listed in the CISA Known Exploited Vulnerabilities catalog on Oct 28, 2026. Federal remediation due: Oct 31, 2026.

Technical details

Technical analysis has not been written for this record yet.

Mitigation & remediation

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.