# 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.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-80615, GHSA-7hmj-qv84-3gcj, UBUNTU-CVE-2026-80615

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80615 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-80615 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-80615/ (Markdown: https://insights.sbomify.com/CVE-2026-80615/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80615
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80615
- OSV: https://osv.dev/vulnerability/CVE-2026-80615

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80615/
Summaries are generated and may contain mistakes; the official description above is the record.