# CVE-2026-64047: net: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring

> An off-by-one error in Linux kernel TLS handling can lead to memory corruption, potentially causing denial of service or code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 19 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-64047, DEBIAN-CVE-2026-64047, GHSA-25cm-2563-466g, UBUNTU-CVE-2026-64047

## What is CVE-2026-64047?

CVE-2026-64047 is a critical vulnerability in Linux kernel, published on 19 Jul 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: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring

When an sk_msg scatterlist ring wraps (sg.end < sg.start),
tls_push_record() chains the tail portion of the ring to the head
using sg_chain(). An extra entry in the sg array is reserved for
this:

  struct sk_msg_sg {
        [...]
        /* The extra two elements:
         * 1) used for chaining the front and sections when the list becomes
         *    partitioned (e.g. end < start). The crypto APIs require the
         *    chaining;
         * 2) to chain tailer SG entries after the message.
         */
        struct scatterlist              data[MAX_MSG_FRAGS + 2];

The current code uses MAX_SKB_FRAGS + 1 as the ring size:

    sg_chain(&msg_pl->sg.data[msg_pl->sg.start],
             MAX_SKB_FRAGS - msg_pl->sg.start + 1,
             msg_pl->sg.data);

This places the chain pointer at

  sg_chain(data[start], (MAX_SKB_FRAGS - msg_start + 1) .. =
  &data[start] + (MAX_SKB_FRAGS - msg_start + 1) - 1 =
  data[start + (MAX_SKB_FRAGS - start + 1) - 1] =
  data[MAX_SKB_FRAGS]

instead of the true last entry. This is likely due to a "race" of
the commit under Fixes landing close to
commit 031097d9e079 ("bpf: sk_msg, zap ingress queue on psock down")

Convert to ARRAY_SIZE and drop the data[start] / - start (as suggested
by Sabrina).

Weakness: CWE-193 (Off-by-one Error), CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-64047?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64047?

Apply the vendor's patch.

## Is CVE-2026-64047 being exploited?

There is no known exploitation of CVE-2026-64047 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64047 and fix it if it is affected.

What it is: CVE-2026-64047 is a critical vulnerability in Linux kernel, published on 19 Jul 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-2026-64047 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-64047/ (Markdown: https://insights.sbomify.com/CVE-2026-64047/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64047
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64047
- OSV: https://osv.dev/vulnerability/CVE-2026-64047

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64047/
Summaries are generated and may contain mistakes; the official description above is the record.