# CVE-2025-68363: bpf: Check skb->transport_header is set in bpf_skb_check_mtu

> A missing check in the Linux kernel BPF helper allows local attackers to trigger a kernel warning or potential crash via crafted network packets.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-73135, BELL-CVE-2025-68363, DEBIAN-CVE-2025-68363, GHSA-xphm-v24c-73f6, ROOT-OS-DEBIAN-12-CVE-2025-68363, ROOT-OS-UBUNTU-2204-CVE-2025-68363, ROOT-OS-UBUNTU-2404-CVE-2025-68363, UBUNTU-CVE-2025-68363

## What is CVE-2025-68363?

CVE-2025-68363 is a vulnerability in Linux, published on 24 Dec 2025. 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:

bpf: Check skb->transport_header is set in bpf_skb_check_mtu

The bpf_skb_check_mtu helper needs to use skb->transport_header when
the BPF_MTU_CHK_SEGS flag is used:

	bpf_skb_check_mtu(skb, ifindex, &mtu_len, 0, BPF_MTU_CHK_SEGS)

The transport_header is not always set. There is a WARN_ON_ONCE
report when CONFIG_DEBUG_NET is enabled + skb->gso_size is set +
bpf_prog_test_run is used:

WARNING: CPU: 1 PID: 2216 at ./include/linux/skbuff.h:3071
 skb_gso_validate_network_len
 bpf_skb_check_mtu
 bpf_prog_3920e25740a41171_tc_chk_segs_flag # A test in the next patch
 bpf_test_run
 bpf_prog_test_run_skb

For a normal ingress skb (not test_run), skb_reset_transport_header
is performed but there is plan to avoid setting it as described in
commit 2170a1f09148 ("net: no longer reset transport_header in __netif_receive_skb_core()").

This patch fixes the bpf helper by checking
skb_transport_header_was_set(). The check is done just before
skb->transport_header is used, to avoid breaking the existing bpf prog.
The WARN_ON_ONCE is limited to bpf_prog_test_run, so targeting bpf-next.

## Which versions are affected by CVE-2025-68363?


## How do I fix CVE-2025-68363?

Apply the vendor's patch.

## Is CVE-2025-68363 being exploited?

There is no known exploitation of CVE-2025-68363 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68363 and fix it if it is affected.

What it is: CVE-2025-68363 is a vulnerability in Linux, published on 24 Dec 2025. 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-2025-68363 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-2025-68363/ (Markdown: https://insights.sbomify.com/CVE-2025-68363/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68363
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68363
- OSV: https://osv.dev/vulnerability/CVE-2025-68363

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68363/
Summaries are generated and may contain mistakes; the official description above is the record.