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

RBRecent Breaches Vulnerability Intelligence·Oct 28, 2026

CVSS 7.8 · High⚠ Actively exploited (CISA KEV)

7.8

CVSS score

High

Severity

Active

CISA KEV

Ransomware use

Oct 31, 2026

Patch deadline

⚠ Exploited in the wild. CISA added CVE-2026-46300 to its Known Exploited Vulnerabilities catalog on Oct 28, 2026, with a federal patch deadline of Oct 31, 2026 — meaning attackers are actively using it. If you run the affected software, patch it immediately.

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.

Details

AffectedLinux · Kernel

WeaknessCWE-787

CVSS base score7.8 (High)

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

PublishedMay 23, 2026

Added to CISA KEVOct 28, 2026

Federal patch deadlineOct 31, 2026

Known ransomware useNot documented

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Frequently asked questions

Is CVE-2026-46300 being actively exploited?

Yes — CISA lists CVE-2026-46300 in its Known Exploited Vulnerabilities (KEV) catalog, so it is confirmed exploited in the wild. Patch it as a priority.

What does CVE-2026-46300 affect?

CVE-2026-46300 affects Linux · Kernel.

How do I fix CVE-2026-46300?

Apply the vendor’s patch for the affected software. The federal patch deadline was Oct 31, 2026. Then check whether your personal data was exposed in any related breach.

References

Official records: NVD · CISA KEV

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