CVE-2026-98306

seg6: set IPSKB_L3SLAVE from IP6SKB_L3SLAVE on IPIP decapsulation

Published Oct 6, 2026 CVSS 3.1 · 7.0 High EPSS < 1% KEV · Not listed

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.

Analysis

Technical impact

The bug in the Linux kernel causes the IPSKB_L3SLAVE flag to remain unset when SRv6 packets undergo IPIP decapsulation on interfaces that belong to a VRF. As a result, sockets bound to these VRF‑enslaved interfaces do not receive the decapsulated packets, while sockets that are not bound still do. This behavior violates the expected VRF isolation guarantee and can lead to the loss of legitimate traffic and possible denial‑of‑service conditions for services that rely on VPN decapsulation.

Affected Systems

All Linux kernels that include SRv6, VRF, and IPIP decapsulation support are affected until the patch that correctly sets the flag is applied. This includes mainstream distribution kernels that have not yet incorporated commit 44930446dde4, as well as custom kernels that use these features.

Risk and Exploitability

The vulnerability is scored 7.0 on CVSS, has an EPSS score of less than 1%, and is not listed in the CISA KEV catalog. It can be exploited remotely when an attacker can inject crafted SRv6/IPv6 traffic that triggers IPIP decapsulation on a VRF‑enslaved interface. The likely attack vector, inferred from the packet handling code path, is network‑based packet injection; the description does not explicitly state the vector, so this inference is based on the affected code. The risk is substantial due to the potential for service disruption and violation of VRF isolation, though the vulnerability does not provide code execution or data compromise.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< 1d9f5c78903dd25a3556229eb716dd465c5f3573
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< 72f410616000d21a0a6ec6c93a60301b9c92e95c
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< e4d7c52f15f572608374947c6c802052e1a2fc82
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< 5130afa025c95faa621adf8bac525baeb2b290d2
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< f8fb4738ccef5f9d107845b05734a56352747b1a
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< ddf60220c925b54a1714c4722fdbdb12833232d0
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< 8c16e1ccc082a3763dfc6bc2d3f658c1a6336f9d
`891ef8dd2a8d14e4e73a81dcdb135b574c57f556`	affected	< 7616242a2b37883f7322aaa1d2bd6cd0fed28315

Linux

affected

Version	Status	Constraints
`4.14`	affected	—
`0`	unaffected	< 4.14
`5.10.271`	unaffected	≤ 5.10.*
`5.15.222`	unaffected	≤ 5.15.*
`6.1.189`	unaffected	≤ 6.1.*
`6.6.158`	unaffected	≤ 6.6.*
`6.12.112`	unaffected	≤ 6.12.*
`6.18.54`	unaffected	≤ 6.18.*
`7.2.8`	unaffected	≤ 7.2.*
`7.3`	unaffected	≤ *

No data.

Vendor Product Versions

Linux

Linux Kernel

Version	Status	Scheme	Platform
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,1d9f5c78903dd25a3556229eb716dd465c5f3573)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,72f410616000d21a0a6ec6c93a60301b9c92e95c)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,e4d7c52f15f572608374947c6c802052e1a2fc82)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,5130afa025c95faa621adf8bac525baeb2b290d2)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,f8fb4738ccef5f9d107845b05734a56352747b1a)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,ddf60220c925b54a1714c4722fdbdb12833232d0)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,8c16e1ccc082a3763dfc6c8b4029de08e9f8c3cd)`	affected	code_commit	—
`[891ef8dd2a8d14e4e73a81dcdb135b574c57f556,7616242a2b37883f7322aaa1d2bd6cd0fed28315)`	affected	code_commit	—

Linux

Linux Kernel

Version	Status	Scheme	Platform
`4.14`	affected	generic	—
`[0,4.14)`	unaffected	semver	—
`[5.10.271,5.11.0)`	unaffected	semver	—
`[5.15.222,5.16.0)`	unaffected	semver	—
`[6.1.189,6.2.0)`	unaffected	semver	—
`[6.6.158,6.7.0)`	unaffected	semver	—
`[6.12.112,6.13.0)`	unaffected	semver	—
`[6.18.54,6.19.0)`	unaffected	semver	—
`[7.2.8,7.3.0)`	unaffected	semver	—
`[7.3-rc4,*]`	unaffected	generic	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Apply a kernel update that includes commit 44930446dde4 or newer, which sets the IPSKB_L3SLAVE flag correctly during IPIP decapsulation.
If a kernel update cannot be applied immediately, disable SRv6 or IPIP decapsulation on any interfaces that belong to a VRF, or remove those interfaces from the VRF until the patch is installed.
Continuously monitor kernel logs and debug output for packet drop or socket lookup failures related to SRv6 traffic to verify that the flag is set correctly after remediation.

Generated by OpenCVE AI on October 11, 2026 at 19:22 UTC.

Tracking

Advisories

Source	ID	Title
Debian DLA	DLA-4841-1	linux security update
Debian DLA	DLA-4850-1	linux-6.12 security update
Debian DSA	DSA-6568-1	linux security update
Ubuntu USN	USN-8961-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9019-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-9020-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9022-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9023-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9024-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9025-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9026-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-9029-1	Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN	USN-9039-1	Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN	USN-9040-1	Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN	USN-9066-1	Linux kernel (HWE) vulnerabilities
Ubuntu USN	USN-9091-1	Linux kernel (NVIDIA Tegra) vulnerabilities

Metrics

No CVSS v4.0

Attack Vector Local

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.184% probability within 30 days)

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98306.mbox
https://git.kernel.org/stable/c/1d9f5c78903dd25a3556229eb716dd465c5f3573
https://git.kernel.org/stable/c/5130afa025c95faa621adf8bac525baeb2b290d2
https://git.kernel.org/stable/c/72f410616000d21a0a6ec6c93a60301b9c92e95c
https://git.kernel.org/stable/c/7616242a2b37883f7322aaa1d2bd6cd0fed28315
https://git.kernel.org/stable/c/8c16e1ccc082a3763dfc6bc2d3f658c1a6336f9d
https://git.kernel.org/stable/c/ddf60220c925b54a1714c4722fdbdb12833232d0
https://git.kernel.org/stable/c/e4d7c52f15f572608374947c6c802052e1a2fc82
https://git.kernel.org/stable/c/f8fb4738ccef5f9d107845b05734a56352747b1a
https://nvd.nist.gov/vuln/detail/CVE-2026-98306
https://www.cve.org/CVERecord?id=CVE-2026-98306

History

Oct 11, 2026 5:30 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses	CWE-665

Oct 11, 2026 12:15 PM Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-653
References		https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98306.mbox https://nvd.nist.gov/vuln/detail/CVE-2026-98306 https://www.cve.org/CVERecord?id=CVE-2026-98306
Metrics	threat_severity `None`	cvssV3_1 `{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}` threat_severity `Moderate`

Oct 6, 2026 8:30 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-665

Oct 6, 2026 6:00 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses	CWE-610

Oct 6, 2026 1:30 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-610

Oct 6, 2026 9:00 AM Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references View changes

Type	Values Removed	Values Added
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.
Title		seg6: set IPSKB_L3SLAVE from IP6SKB_L3SLAVE on IPIP decapsulation
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/1d9f5c78903dd25a3556229eb716dd465c5f3573 https://git.kernel.org/stable/c/5130afa025c95faa621adf8bac525baeb2b290d2 https://git.kernel.org/stable/c/72f410616000d21a0a6ec6c93a60301b9c92e95c https://git.kernel.org/stable/c/7616242a2b37883f7322aaa1d2bd6cd0fed28315 https://git.kernel.org/stable/c/8c16e1ccc082a3763dfc6bc2d3f658c1a6336f9d https://git.kernel.org/stable/c/ddf60220c925b54a1714c4722fdbdb12833232d0 https://git.kernel.org/stable/c/e4d7c52f15f572608374947c6c802052e1a2fc82 https://git.kernel.org/stable/c/f8fb4738ccef5f9d107845b05734a56352747b1a