# CVE-2025-68363

## Summary

- **CVE ID:** CVE-2025-68363
- **Severity:** UNKNOWN
- **CVSS Score:** 1.51
- **CWE:** N/A
- **Published:** Dec 24, 2025
- **Last Modified:** Sep 17, 2026

## 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.

## Affected Products

- Linux — Linux (34b2021cc61642d61c3cf943d9e71925b827941b)
- Linux — Linux (5.12)
- Linux — Linux (0)
- Linux — Linux (6.1.160)
- Linux — Linux (6.6.120)
- Linux — Linux (6.12.63)
- Linux — Linux (6.17.13)
- Linux — Linux (6.18.2)
- Linux — Linux (6.19)

## References

- [CNA](https://git.kernel.org/stable/c/b3171a5e4622e915e94599a55f4964078bdec27e)
- [CNA](https://git.kernel.org/stable/c/97b876fa88322625228792cf7a5fd77531815a80)
- [CNA](https://git.kernel.org/stable/c/30ce906557a21adef4cba5901c8e995dc18263a9)
- [CNA](https://git.kernel.org/stable/c/1c30e4afc5507f0069cc09bd561e510e4d97fbf7)
- [CNA](https://git.kernel.org/stable/c/942268e2726ac7f16e3ec49dbfbbbe7cf5af9da5)
- [CNA](https://git.kernel.org/stable/c/d946f3c98328171fa50ddb908593cf833587f725)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.20%
- **EPSS Percentile:** 10.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._