# CVE-2026-98493: net: ipconfig: bound DHCP option construction

> A buffer overflow in the Linux kernel DHCP option construction allows a local attacker to cause a system panic via crafted hostname and vendor-class options.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-108671, BELL-CVE-2026-98493, DEBIAN-CVE-2026-98493, GHSA-x4fq-3fw2-872x, UBUNTU-CVE-2026-98493

## What is CVE-2026-98493?

CVE-2026-98493 is a memory corruption vulnerability in Linux, published on 18 Oct 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:

net: ipconfig: bound DHCP option construction

ic_dhcp_init_options() appends the hostname (option 12), vendor-class
(option 60) and client-ID (option 61) options into the fixed 312-byte
bootp_pkt.exten[] buffer.  Only the client-ID branch checked the
remaining space; the hostname and vendor-class writes were unbounded.

A 64-byte hostname together with the maximum 252-byte dhcpclass=
identifier needs 18 + (2 + 64) + (2 + 252) = 338 of the 312 available
bytes even before the terminating END marker, so the vendor-class memcpy
runs past the end of exten[].  With CONFIG_FORTIFY_SOURCE this is
reported as a field-spanning write and, when the kernel is booted with
panic_on_warn=1, aborts boot with a panic.

Route the optional options through a common helper that makes sure the
option, its 2-byte header and the END marker all fit and drops an option
that would not.  Configurations with short options keep sending exactly
the same bytes as before.

## Which versions are affected by CVE-2026-98493?


## How do I fix CVE-2026-98493?

Apply the vendor's patch.

## Is CVE-2026-98493 being exploited?

There is no known exploitation of CVE-2026-98493 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98493 and fix it if it is affected.

What it is: CVE-2026-98493 is a memory corruption vulnerability in Linux, published on 18 Oct 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-2026-98493 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-2026-98493/ (Markdown: https://insights.sbomify.com/CVE-2026-98493/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98493
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98493
- OSV: https://osv.dev/vulnerability/CVE-2026-98493

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98493/
Summaries are generated and may contain mistakes; the official description above is the record.