CVE-2026-46300
Linux Kernel Missing Initialization of a Variable Vulnerability
CISA due Oct 31, 2026
- Linux Kernel
- High
- CVSS 7.8
- EPSS 10.19%
- Fixed version listed
Summary
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.
From CISA's Known Exploited Vulnerabilities catalog.
Read the original description
CVE record
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.
What to do
Fixed version listed
- 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.
- CISA deadline for US federal agencies
- Oct 31, 2026
Affected products
| Product | Affected | Fixed in |
|---|---|---|
| Linux Linux | Only in the CVE record | Only in the CVE record |
| Linux Linux | every version except: before 3.9; from 5.10.257 through 5.10.*; from 5.15.208 through 5.15.*; from 6.1.174 through 6.1.*; from 6.6.141 through 6.6.*; from 6.12.91 through 6.12.*; from 6.18.33 through 6.18.*; from 7.0.10 through 7.0.*; from 7.1 on | 5.10.257, 5.15.208, 6.1.174, 6.6.141, 6.12.91, 6.18.33, 7.0.10, 7.1 |
The CVE record lists 8 ranges this page cannot state exactly.
Advisories and fixes
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
- Vendor advisory access.redhat.com
Scores and signals
- Exploitation
- Exploited in the wild
- Severity
- High, CVSS 7.8 (v3.1, scored by Linux)
- EPSS
- 10.19% chance of exploitation in the next 30 days (EPSS from FIRST, as of Oct 28, 2026)
- CISA's SSVC decision points
- Exploitation: none. Automatable: no. Technical impact: total. As of Oct 16, 2026.
- Weakness
- CWE-456: Missing Initialization of a Variable
- Vendor
- Linux, Kernel
Timeline
- Added to CISA's Known Exploited Vulnerabilities catalog: exploited in the wild. US federal agencies must remediate by 2026-10-31.