CVE-2026-80615
largeFalse-positive memcpy overflow warning in Linux kernel tunnel metadata (dst_metadata)
CVE-2026-80615 is a flaw in the Linux kernel's tunnel metadata handling code (net/dst_metadata): when metadata_dst_alloc() allocates the destination structure, its __counted_by option length is initialized to zero, so a later single memcpy that copies the tunnel info plus options in tun_dst_unclone() is flagged by the compiler's fortify checks as a buffer overflow (e.g., a 104-byte write into a 96-byte buffer). The warning is observed in the skb_tunnel_info_unclone() path during GENEVE transmit (geneve_xmit) on kernels built with clang and source fortification enabled, meaning remotely delivered traffic traversing a GENEVE/tunnel-metadata overlay can trigger it. The rated impact is primarily availability (CVSS 3.1 8.2, AV:N with high availability impact): the fortify report raises a kernel warning and stack trace that can disrupt packet processing, and can crash the host if warnings are configured to panic; confidentiality impact is rated low and integrity unaffected. Affected systems are Linux kernels containing this code (specific version ranges are not stated in the available data) that perform tunnel-metadata uncloning, notably SDN/overlay deployments using GENEVE. No public proof-of-concept, exploitation in the wild, or CISA KEV listing is known, and EPSS puts 30-day exploitation probability at about 0.4%.
What to do: Apply the kernel update from your distribution or vendor that includes the upstream dst_metadata fix (which copies the tunnel header and options in two stages so the length is known at copy time) once a fixed version is published; the source data does not state a fixed version number. Prioritize hosts that originate or forward GENEVE/tunnel-metadata traffic on clang-built kernels with fortification, check logs for 'memcpy: detected buffer overflow' warnings from skb_tunnel_info_unclone/geneve_xmit, and consider avoiding panic_on_warn on affected overlay hosts until patched.
| Linux kernel (net: dst_metadata / tun_dst_unclone, GENEVE tunnel-metadata path) | — |
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
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.
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
In the news0 stories
No ingested article mentions this CVE yet.