# CVE-2026-74597: ip6_tunnel: clear skb2->cb[] in ip6ip6_err()

> A memory corruption vulnerability in the Linux kernel's IPv6 tunnel error handling allows attackers to corrupt kernel memory, potentially leading to code execution or system crashes.

- **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:** 22 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97350, BELL-CVE-2026-74597, DEBIAN-CVE-2026-74597, GHSA-2fqw-fh97-qvmc, UBUNTU-CVE-2026-74597

## What is CVE-2026-74597?

CVE-2026-74597 is a critical memory corruption vulnerability in Linux, published on 22 Aug 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:

ip6_tunnel: clear skb2->cb[] in ip6ip6_err()

ip6ip6_err() clones an outer IPv6 ICMP error skb, pulls it to the
quoted inner IPv6 packet, and then passes the clone to icmpv6_send().
The clone still carries the outer packet's inet6_skb_parm in skb->cb.

If the outer packet had a Home Address Option, IP6CB(skb2)->dsthao
remains non-zero after skb_pull(). icmpv6_send() later calls
mip6_addr_swap(), which uses that stale dsthao offset against the quoted
inner packet. A malformed inner destination-options header can then make
the HAO lookup and address swap run past the end of the quoted packet
and corrupt skb_shared_info.

Clear skb2->cb[] before pulling the quoted inner IPv6 packet so the
reply path does not reuse metadata left by the outer IPv6 stack.

## Which versions are affected by CVE-2026-74597?


## How do I fix CVE-2026-74597?

Apply the vendor's patch.

## Is CVE-2026-74597 being exploited?

There is no known exploitation of CVE-2026-74597 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74597 and fix it if it is affected.

What it is: CVE-2026-74597 is a critical memory corruption vulnerability in Linux, published on 22 Aug 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-2026-74597 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-2026-74597/ (Markdown: https://insights.sbomify.com/CVE-2026-74597/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74597
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74597
- OSV: https://osv.dev/vulnerability/CVE-2026-74597

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74597/
Summaries are generated and may contain mistakes; the official description above is the record.