# CVE-2026-68302: amt: re-read skb header pointers after every pull

> A use-after-free vulnerability in the Linux kernel's Automatic Multicast Tunneling module allows attackers to cause denial of service or execute arbitrary code.

- **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:** 10 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** BELL-CVE-2026-68302, DEBIAN-CVE-2026-68302, GHSA-9gq3-j787-cjhr, UBUNTU-CVE-2026-68302

## What is CVE-2026-68302?

CVE-2026-68302 is a critical use after free vulnerability in Linux, published on 10 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:

amt: re-read skb header pointers after every pull

Several AMT receive and transmit paths cache a pointer into the skb head
(ip_hdr(), ipv6_hdr(), eth_hdr() or the AMT message header) and then call
a helper that can reallocate that head before the cached pointer is used
again.  pskb_may_pull(), ip_mc_may_pull(), ipv6_mc_may_pull(),
iptunnel_pull_header(), ip_mc_check_igmp() and ipv6_mc_check_mld() can all
free the old head and move the data, so a pointer taken before the call
dangles afterwards and the later access is a use-after-free of the freed
head.

The affected sites are:

  amt_rcv() caches ip_hdr() before amt_parse_type() pulls, then reads
  iph->saddr.

  amt_dev_xmit() caches ip_hdr()/ipv6_hdr() before ip_mc_check_igmp()/
  ipv6_mc_check_mld() and pskb_may_pull(), then reads the group address.

  amt_multicast_data_handler() caches eth_hdr() before pskb_may_pull(),
  then writes the L2 header.

  amt_membership_query_handler() caches the AMT header, the outer and
  inner eth_hdr() and ip_hdr() before iptunnel_pull_header() and several
  pulls, then reads and writes them.

  amt_igmpv3_report_handler() and amt_mldv2_report_handler() cache
  ip_hdr()/ipv6_hdr() and the current group record and read the record
  count from the report header inside the record loop, across the
  *_mc_may_pull() calls.

  amt_update_handler() caches ip_hdr() and the AMT membership-update
  header before pskb_may_pull(), iptunnel_pull_header(),
  ip_mc_check_igmp() and the report handler, then reads iph->daddr and
  amtmu->nonce / amtmu->response_mac.

Fix each site by either snapshotting the scalar that is used after the
pull before the first pull runs, or re-deriving the header pointer from
the skb after the last pull that can move the head.  Values that are
stable across the pull (source and group address, the response MAC and
nonce, the record count, the outer source MAC) are snapshotted; pointers
that are written through or read repeatedly are re-derived.

## Which versions are affected by CVE-2026-68302?


## How do I fix CVE-2026-68302?

Apply the vendor's patch.

## Is CVE-2026-68302 being exploited?

There is no known exploitation of CVE-2026-68302 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68302 and fix it if it is affected.

What it is: CVE-2026-68302 is a critical use after free vulnerability in Linux, published on 10 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-2026-68302 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-2026-68302/ (Markdown: https://insights.sbomify.com/CVE-2026-68302/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68302
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68302
- OSV: https://osv.dev/vulnerability/CVE-2026-68302

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68302/
Summaries are generated and may contain mistakes; the official description above is the record.