CVE-2026-98306: Linux kernel · seg6: set IPSKB_L3SLAVE from IP6SKB_L3SLAVE on IPIP decapsulation
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 28 Oct 2026, 01:27 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
Exploitation evidence
Disclosed: evidence found.
CVE published 6 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
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.
References
- ubuntu.com/security/CVE-2026-98306 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-98306 (opens in a new tab)
- git.kernel.org/linus/7616242a2b37883f7322aaa1d2bd6cd0fed28315 (opens in a new tab)
- git.kernel.org/stable/c/1d9f5c78903dd25a3556229eb716dd465c5f3573 (opens in a new tab)
- git.kernel.org/stable/c/5130afa025c95faa621adf8bac525baeb2b290d2 (opens in a new tab)
- git.kernel.org/stable/c/72f410616000d21a0a6ec6c93a60301b9c92e95c (opens in a new tab)
- git.kernel.org/stable/c/7616242a2b37883f7322aaa1d2bd6cd0fed28315 (opens in a new tab)
- git.kernel.org/stable/c/8c16e1ccc082a3763dfc6bc2d3f658c1a6336f9d (opens in a new tab)
- git.kernel.org/stable/c/ddf60220c925b54a1714c4722fdbdb12833232d0 (opens in a new tab)
- git.kernel.org/stable/c/e4d7c52f15f572608374947c6c802052e1a2fc82 (opens in a new tab)
- git.kernel.org/stable/c/f8fb4738ccef5f9d107845b05734a56352747b1a (opens in a new tab)