CVE-2026-43040
HIGHDescription
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: ndisc: fix ndisc_ra_useropt to initialize nduseropt_padX fields to zero to prevent an info-leak When processing Router Advertisements with user options the kernel builds an RTM_NEWNDUSEROPT netlink message. The nduseroptmsg struct has three padding fields that are never zeroed and can leak kernel data The fix is simple, just zeroes the padding fields.
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 2% of all known CVEs.
References
Related Vulnerabilities
Other CWE-909 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2018-14647 | High | 7.5 | 11% | - | Fix |
| CVE-2019-9639 | High | 7.5 | 8.2% | - | Fix |
| CVE-2018-10811 | High | 7.5 | 6.2% | - | Fix |
| CVE-2020-12352 | Medium | 6.5 | 5.7% | - | Fix |
| CVE-2019-3804 | High | 7.5 | 4.9% | - | Fix |
| CVE-2020-16932 | High | 7.8 | 4.8% | - | - |
Common questions
How do I fix CVE-2026-43040?
Published advisories record a fix for 247 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-43040 being actively exploited?
Not that we know of. CVE-2026-43040 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.12% is the estimated probability that it will be exploited in the next 30 days. That is higher than 2% of all scored CVEs.
How severe is CVE-2026-43040?
CVE-2026-43040 has a CVSS v3 base score of 7.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-43040 affect?
Published advisories record a fix for linux (Debian), linux (Ubuntu), linux-aws (Ubuntu), linux-aws-5.15 (Ubuntu), and 243 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-14.