CVE-2026-89776 vxlan: vnifilter: enforce exact length of GROUP/GROUP6 attributes
A local attacker can trigger a kernel memory over-read in VXLAN VNI filters, disclosing uninitialized kernel memory via netlink responses.
- 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-2026-89776?
CVE-2026-89776 is a vulnerability in Linux, published on 16 Sep 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:
vxlan: vnifilter: enforce exact length of GROUP/GROUP6 attributes
The VXLAN VNI filter entry policy declares the GROUP/GROUP6 address attributes as NLA_BINARY with only a maximum length, so validate_nla() accepts a payload shorter than the address. The GROUP consumer reads it with nla_get_in_addr(), an unconditional 4-byte load, so a short attribute over-reads up to 3 bytes of uninitialised slab data, which are stored into remote_ip and echoed back via RTM_GETTUNNEL, disclosing kernel memory.
Switch both entries to NLA_POLICY_EXACT_LEN() so the validator rejects any GROUP/GROUP6 that is not exactly 4 / 16 bytes; a valid address is always sent at full width.
Which versions are affected by CVE-2026-89776?
How do I fix CVE-2026-89776?
Apply the vendor's patch.
Is CVE-2026-89776 being exploited?
There is no known exploitation of CVE-2026-89776 in the wild and no public exploit code.
Sources
Also known as AZL-101391, BELL-CVE-2026-89776, DEBIAN-CVE-2026-89776, GHSA-vf8c-65h3-589v, UBUNTU-CVE-2026-89776.