# CVE-2026-80848: xfrm: espintcp: fix UAF during close

> A race condition in the Linux kernel's espintcp module allows attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-99564, BELL-CVE-2026-80848, DEBIAN-CVE-2026-80848, GHSA-gvv5-3h67-3922, UBUNTU-CVE-2026-80848

## What is CVE-2026-80848?

CVE-2026-80848 is an use after free vulnerability in Linux, published on 4 Sep 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:

xfrm: espintcp: fix UAF during close

ZDI reported and analyzed a race condition during close for espintcp
sockets:

    espintcp_close() frees emsg->skb via kfree_skb() without holding
    any socket lock. Concurrently, the xfrm_trans_reinject work queue
    invokes esp_output_tcp_finish() -> espintcp_push_skb() ->
    espintcp_push_msgs() -> skb_send_sock_locked(), which reads the
    same skb as a data source.

Fix this by adding a synchronize_rcu() call after resetting sk_prot,
since esp_output_tcp_finish() runs under RCU and won't use a socket
with sk_prot == &tcp_prot.  Simply taking the socket lock in
espintcp_close() could lead to leaks, if esp_output_tcp_finish()
re-adds an skb in the slot we just freed. After this, the existing
barrier() is no longer needed.

## Which versions are affected by CVE-2026-80848?


## How do I fix CVE-2026-80848?

Apply the vendor's patch.

## Is CVE-2026-80848 being exploited?

There is no known exploitation of CVE-2026-80848 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80848 and fix it if it is affected.

What it is: CVE-2026-80848 is an use after free vulnerability in Linux, published on 4 Sep 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-2026-80848 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-2026-80848/ (Markdown: https://insights.sbomify.com/CVE-2026-80848/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80848
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80848
- OSV: https://osv.dev/vulnerability/CVE-2026-80848

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80848/
Summaries are generated and may contain mistakes; the official description above is the record.