CVE-2026-43040 net: ipv6: ndisc: fix ndisc_ra_useropt to initialize nduseropt_padX fields to zero to prevent an info-leak
Uninitialized padding fields in IPv6 Router Advertisement processing leak kernel memory contents to local users via netlink messages.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43040?
CVE-2026-43040 is a high-severity vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-909
Which versions are affected by CVE-2026-43040?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43040?
Apply the vendor's patch.
Is CVE-2026-43040 being exploited?
There is no known exploitation of CVE-2026-43040 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43040, DEBIAN-CVE-2026-43040, GHSA-59pc-r9mr-h2pv, ROOT-OS-DEBIAN-11-CVE-2026-43040, ROOT-OS-UBUNTU-2204-CVE-2026-43040, ROOT-OS-UBUNTU-2404-CVE-2026-43040 and 1 more.