# CVE-2026-93105: esp: do not unref managed frag pages in esp_ssg_unref()

> A missing guard in the Linux kernel ESP implementation causes premature page freeing for managed fragments, potentially leading to use-after-free and code execution.

- **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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102042, BELL-CVE-2026-93105, DEBIAN-CVE-2026-93105, GHSA-m483-33mw-4p7w, UBUNTU-CVE-2026-93105

## What is CVE-2026-93105?

CVE-2026-93105 is a high-severity use after free vulnerability in Linux, published on 17 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:

esp: do not unref managed frag pages in esp_ssg_unref()

esp_ssg_unref() releases the page references held on the source
scatterlist after the AEAD operation completes.  It calls
skb_page_unref() on every frag page for an out-of-place transform
(req->src != req->dst), and in the error path of esp_output_tail()
(already_unref == true) on the request's own scatterlist.

This is wrong when the skb carries managed frags
(SKBFL_MANAGED_FRAG_REFS).  Managed frags are owned by a zerocopy ubuf
and the skb does not hold a per-frag page reference; io_uring SEND_ZC
with a registered buffer attaches the bvec pages this way via
io_sg_from_iter().  The rest of the stack honours this invariant:
skb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS
is set, and skb_zcopy_managed() is the guard used at the other unref
sites.

esp_ssg_unref() is missing that guard, so for a managed-frag skb it
drops a page reference the skb never acquired.  This can underflow the
page reference count and free a page that is still in use.

Guard the function with skb_zcopy_managed() so both unref paths are
skipped for managed-frag skbs, matching skb_release_data().

## Which versions are affected by CVE-2026-93105?


## How do I fix CVE-2026-93105?

Apply the vendor's patch.

## Is CVE-2026-93105 being exploited?

There is no known exploitation of CVE-2026-93105 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93105 and fix it if it is affected.

What it is: CVE-2026-93105 is a high-severity use after free vulnerability in Linux, published on 17 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-2026-93105 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-2026-93105/ (Markdown: https://insights.sbomify.com/CVE-2026-93105/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93105
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93105
- OSV: https://osv.dev/vulnerability/CVE-2026-93105

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93105/
Summaries are generated and may contain mistakes; the official description above is the record.