# CVE-2026-89487: openvswitch: only skb_tx_error() a packet we are about to drop

> An attacker can trigger a page-cache write primitive in the Linux kernel via Open vSwitch, potentially leading to privilege escalation or data modification.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100568, BELL-CVE-2026-89487, DEBIAN-CVE-2026-89487, GHSA-7xvh-m494-6w6x, UBUNTU-CVE-2026-89487

## What is CVE-2026-89487?

CVE-2026-89487 is a high-severity memory corruption vulnerability in Linux, published on 11 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:

openvswitch: only skb_tx_error() a packet we are about to drop

queue_userspace_packet() borrows the packet skb -- it only copies it into
a private netlink message (user_skb) and does not own it; on return
do_execute_actions() keeps forwarding it through the flow's remaining
actions. Its error path nevertheless calls skb_tx_error(skb), which via
skb_zcopy_clear() does skb_shinfo(skb)->flags &= ~SKBFL_ALL_ZEROCOPY,
stripping SKBFL_SHARED_FRAG from that live skb (skb_tx_error()'s kerneldoc
says "skb must be freed afterwards").

For a MSG_ZEROCOPY skb carrying page-cache frags, SKBFL_SHARED_FRAG is
what makes esp_input() skb_cow_data() before in-place AEAD; once it is
stripped a later local ESP-in-UDP delivery decrypts in place over pages
the sender does not own -- an unprivileged page-cache write (the
"Fragnesia" primitive).
do_execute_actions() ignores output_userspace()'s return value, so any
action after a failed USERSPACE upcall inherits the stripped skb.

Move the skb_tx_error() to the flow-miss drop path - the "default"
branch of ovs_dp_process_packet()'s switch(error), before kfree_skb().

The call has been here since commit 36d5fe6a0007 ("core, nfqueue,
openvswitch: Orphan frags in skb_zerocopy and handle errors") but was
harmless until esp_input() began relying on SKBFL_SHARED_FRAG to gate
in-place decrypt; only then did stripping it on a still-forwarded skb
become a page-cache write primitive.

## Which versions are affected by CVE-2026-89487?


## How do I fix CVE-2026-89487?

Apply the vendor's patch.

## Is CVE-2026-89487 being exploited?

There is no known exploitation of CVE-2026-89487 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89487 and fix it if it is affected.

What it is: CVE-2026-89487 is a high-severity memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89487 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-2026-89487/ (Markdown: https://insights.sbomify.com/CVE-2026-89487/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89487
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89487
- OSV: https://osv.dev/vulnerability/CVE-2026-89487

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89487/
Summaries are generated and may contain mistakes; the official description above is the record.