# CVE-2026-53004: sctp: fix OOB write to userspace in sctp_getsockopt_peer_auth_chunks

> An out-of-bounds write in the Linux kernel SCTP module allows an unprivileged local user to corrupt adjacent userspace memory via a crafted getsockopt call.

- **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:** 24 Jun 2026
- **Updated:** 24 Jun 2026
- **Also known as:** BELL-CVE-2026-53004, DEBIAN-CVE-2026-53004, GHSA-79rv-wg4r-99gp, ROOT-OS-DEBIAN-11-CVE-2026-53004, ROOT-OS-DEBIAN-12-CVE-2026-53004, ROOT-OS-UBUNTU-2204-CVE-2026-53004, ROOT-OS-UBUNTU-2404-CVE-2026-53004, UBUNTU-CVE-2026-53004

## What is CVE-2026-53004?

CVE-2026-53004 is a high-severity memory corruption vulnerability in Linux kernel, published on 24 Jun 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:

sctp: fix OOB write to userspace in sctp_getsockopt_peer_auth_chunks

sctp_getsockopt_peer_auth_chunks() checks that the caller's optval
buffer is large enough for the peer AUTH chunk list with

    if (len < num_chunks)
            return -EINVAL;

but then writes num_chunks bytes to p->gauth_chunks, which lives
at offset offsetof(struct sctp_authchunks, gauth_chunks) == 8
inside optval.  The check is missing the sizeof(struct
sctp_authchunks) = 8-byte header.  When the caller supplies
len == num_chunks (for any num_chunks > 0) the test passes but
copy_to_user() writes sizeof(struct sctp_authchunks) = 8 bytes
past the declared buffer.

The sibling function sctp_getsockopt_local_auth_chunks() at the
next line already has the correct check:

    if (len < sizeof(struct sctp_authchunks) + num_chunks)
            return -EINVAL;

Align the peer variant with its sibling.

Reproducer confirms on v7.0-13-generic: an unprivileged userspace
caller that opens a loopback SCTP association with AUTH enabled,
queries num_chunks with a short optval, then issues the real
getsockopt with len == num_chunks and sentinel bytes painted past
the buffer observes those sentinel bytes overwritten with the
peer's AUTH chunk type.  The bytes written are under the peer's
control but land in the caller's own userspace; this is not a
kernel memory corruption, but it is a kernel-side contract
violation that can silently corrupt adjacent userspace data.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-53004?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53004?

Apply the vendor's patch.

## Is CVE-2026-53004 being exploited?

There is no known exploitation of CVE-2026-53004 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-2026-53004 and fix it if it is affected.

What it is: CVE-2026-53004 is a high-severity memory corruption vulnerability in Linux kernel, published on 24 Jun 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-2026-53004 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-2026-53004/ (Markdown: https://insights.sbomify.com/CVE-2026-53004/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53004
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53004
- OSV: https://osv.dev/vulnerability/CVE-2026-53004

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53004/
Summaries are generated and may contain mistakes; the official description above is the record.