CVE-2026-63999: ethtool: rss: fix indir_table and hkey leak on get_rxfh failure

criticalCVSS 9.8CVE-2026-63999

CSIRTS triage

Other

What: This issue involves a leak of indirect table and hash key information on get_rxfh failure.
Who is affected: Deployments using the ethtool feature in affected versions.
Urgency: Remediation is urgent due to the critical severity and potential for exploitation.
Action: Update to the latest version of ethtool to fix this issue.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: critical — CVSS 9.8
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63999

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-639990.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 6% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-63999	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

highUSN-8618-1: Linux kernel vulnerabilitiesubuntu
highUSN-8603-1: Linux kernel (Azure) vulnerabilitiesubuntu
highUSN-8593-1: Linux kernel vulnerabilitiesubuntu
unknownCVE-2026-63999: In the Linux kernel, the following vulnerability has been resolved: ethtool: rss: fix indir_ta…nvd

Recent advisories for ethtool

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownCVE-2026-64526: In the Linux kernel, the following vulnerability has been resolved: ethtool: tsconfig: fix mis…nvd · 2026-07-25
unknownCVE-2026-64228: In the Linux kernel, the following vulnerability has been resolved: net: ethtool: phy: avoid N…nvd · 2026-07-24
unknownCVE-2026-64121: In the Linux kernel, the following vulnerability has been resolved: net: ifb: report ethtool s…nvd · 2026-07-19
unknownCVE-2026-64120: In the Linux kernel, the following vulnerability has been resolved: net: ethtool: fix NULL poi…nvd · 2026-07-19
unknownCVE-2026-63999: In the Linux kernel, the following vulnerability has been resolved: ethtool: rss: fix indir_ta…nvd · 2026-07-19
unknownCVE-2026-63998: In the Linux kernel, the following vulnerability has been resolved: ethtool: module: call ethn…nvd · 2026-07-19