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

Vulnerability summary

CVE-2026-46300 is a high (CVSS 7.8) Out-of-bounds Write vulnerability in Linux Kernel. It is known to be exploited: CISA lists it, first on 28-10-2026. EPSS estimates a 16.13% chance of exploitation in the next 30 days, higher than 96.9% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 23-05-2026
   PublishedVulnerability first disclosed.
2. 28-10-2026
   Added to CISA KEVExploitedLinux Kernel Missing Initialization of a Variable Vulnerability
3. 29-10-2026
   Last modifiedVulnerability information updated.
4. 31-10-2026
   CISA remediation dueDeadline passedApply mitigations per vendor instructions.

Description

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.

• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.
• CWE-456Missing Initialization of a VariableThe product does not initialize critical variables.
• CWE-123Write-what-where ConditionAny condition where the attacker has the ability to write an arbitrary value to an arbitrary location, often as the result of a buffer overflow.