# CVE-2026-98402: net: icmp: avoid invalid transport header access in icmp_send tracepoint

> A missing check in the Linux kernel ICMP tracepoint causes a null pointer dereference when processing non-UDP packets, leading to a system crash.

- **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:** 14 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108113, BELL-CVE-2026-98402, DEBIAN-CVE-2026-98402, GHSA-ggf3-fm45-ccm2, UBUNTU-CVE-2026-98402

## What is CVE-2026-98402?

CVE-2026-98402 is a vulnerability in Linux, published on 14 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: icmp: avoid invalid transport header access in icmp_send tracepoint

syzbot reported a WARNING triggered by DEBUG_NET_WARN_ON_ONCE():

 WARNING: at skb_transport_header include/linux/skbuff.h:3087 [inline]
 WARNING: at udp_hdr include/linux/udp.h:23 [inline]
 WARNING: at do_trace_event_raw_event_icmp_send include/trace/events/icmp.h:30 [inline]
 WARNING: at trace_event_raw_event_icmp_send+0x48c/0x6ec include/trace/events/icmp.h:11
 Call trace:
  skb_transport_header include/linux/skbuff.h:3087 [inline]
  udp_hdr include/linux/udp.h:23 [inline]
  do_trace_event_raw_event_icmp_send include/trace/events/icmp.h:30 [inline]
  trace_event_raw_event_icmp_send+0x48c/0x6ec include/trace/events/icmp.h:11
  __traceiter_icmp_send include/trace/events/icmp.h:11 [inline]
  __do_trace_icmp_send include/trace/events/icmp.h:11 [inline]
  trace_icmp_send+0x320/0x49c include/trace/events/icmp.h:11
  __icmp_send+0xcfc/0x11d8 net/ipv4/icmp.c:1013
  ipv4_send_dest_unreach net/ipv4/route.c:1280 [inline]
  ipv4_link_failure+0x57c/0x8dc net/ipv4/route.c:1287
  dst_link_failure include/net/dst.h:438 [inline]
  vti_tunnel_xmit+0xe40/0x17a4 net/ipv4/ip_vti.c:307

TP_fast_assign() unconditionally calls udp_hdr(skb) before checking
whether the packet is UDP. Furthermore, __icmp_send() can be invoked
from paths (e.g., link failures, ARP errors, forwarding, AF_PACKET)
where skb->transport_header was never initialized (~0U).

Under CONFIG_DEBUG_NET=y, calling skb_transport_header(skb) triggers
DEBUG_NET_WARN_ON_ONCE(!skb_transport_header_was_set(skb)).

Fix this by:
1. Only parsing transport info when iph->protocol == IPPROTO_UDP.
2. Using skb_header_pointer() at skb_network_offset(skb) + (iph->ihl << 2)
   to safely fetch the UDP header without assuming transport_header is set.

## Which versions are affected by CVE-2026-98402?


## How do I fix CVE-2026-98402?

Apply the vendor's patch.

## Is CVE-2026-98402 being exploited?

There is no known exploitation of CVE-2026-98402 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98402 and fix it if it is affected.

What it is: CVE-2026-98402 is a vulnerability in Linux, published on 14 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-2026-98402 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-2026-98402/ (Markdown: https://insights.sbomify.com/CVE-2026-98402/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98402
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98402
- OSV: https://osv.dev/vulnerability/CVE-2026-98402

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98402/
Summaries are generated and may contain mistakes; the official description above is the record.