CVE-2026-80615 net: dst_metadata: fix false-positive memcpy overflow in tun_dst_unclone
A false-positive buffer overflow warning in the Linux kernel's tunneling code can cause a kernel panic when compiled with specific clang fortification settings.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80615?
CVE-2026-80615 is a high-severity vulnerability in Linux, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: dst_metadata: fix false-positive memcpy overflow in tun_dst_unclone
kmalloc_flex() in metadata_dst_alloc() sets __counted_by for the structure to the options_len, which is then initialized to zero. Later, we're initializing the structure by copying the tunnel info together with the options, and this triggers a warning for a potential memcpy overflow, since the compiler estimates that the options can't fit into the structure, even though the memory for them is actually allocated.
memcpy: detected buffer overflow: 104 byte write of buffer size 96 WARNING: CPU: X PID: Y at lib/string_helpers.c:1036 __fortify_report skb_tunnel_info_unclone+0x179/0x190 geneve_xmit+0x7fe/0xe00
The issue is triggered when built with clang and source fortification.
Fix that by doing the copy in two stages: first - the main data with the options_len, then the options. This way the correct length should be known at the time of the copy.
It would be better if the options_len never changed after allocation, but the allocation code is a little separate from the initialization and it would be awkward and potentially dangerous to return a struct with options_len set to a non-zero value from the metadata_dst_alloc().
Another option would be to use ip_tunnel_info_opts_set(), but it is doing too many unnecessary operations for the use case here.
Which versions are affected by CVE-2026-80615?
How do I fix CVE-2026-80615?
Apply the vendor's patch.
Is CVE-2026-80615 being exploited?
There is no known exploitation of CVE-2026-80615 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-80615, GHSA-7hmj-qv84-3gcj, UBUNTU-CVE-2026-80615.