# CVE-2026-98573: net: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6()

> An integer underflow in the Linux kernel's IPv6 checksum setup allows remote attackers to cause memory corruption or denial of service via crafted packets.

- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-109367, BELL-CVE-2026-98573, DEBIAN-CVE-2026-98573, GHSA-23rj-wp7f-556g, UBUNTU-CVE-2026-98573

## What is CVE-2026-98573?

CVE-2026-98573 is a vulnerability in Linux, published on 18 Oct 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: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6()

skb_maybe_pull_tail() subtracts skb_headlen(skb) from the unsigned max
argument and passes the result to __pskb_pull_tail() as a signed int.  The
function does not ensure that max is at least skb_headlen(skb).

This can happen while parsing IPv6 extension headers when an skb already
has a linear area larger than MAX_IPV6_HDR_LEN.  Once the parser needs data
beyond the linear area, max - skb_headlen(skb) wraps and is converted to a
negative delta.  __pskb_pull_tail() then passes that negative length to
skb_copy_bits(), where it can become a very large copy length.

Pass the requested length itself as the pull bound at the three
extension-header call sites, so the delta can no longer go negative.

## Which versions are affected by CVE-2026-98573?


## How do I fix CVE-2026-98573?

Apply the vendor's patch.

## Is CVE-2026-98573 being exploited?

There is no known exploitation of CVE-2026-98573 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98573 and fix it if it is affected.

What it is: CVE-2026-98573 is a vulnerability in Linux, published on 18 Oct 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-2026-98573 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-2026-98573/ (Markdown: https://insights.sbomify.com/CVE-2026-98573/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98573
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98573
- OSV: https://osv.dev/vulnerability/CVE-2026-98573

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98573/
Summaries are generated and may contain mistakes; the official description above is the record.