seg6: reset IP6CB after IPv6 decapsulation

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80976
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:03 UTC
Updated2026-09-14 13:18:52 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: seg6: reset IP6CB after IPv6 decapsulation decap_and_validate() pulls the outer SRv6 headers and makes the inner packet the skb network header. The IPv6 control block still contains values collected while parsing the outer packet, including nhoff and extension-header flags. End.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6 input path. An unprivileged user can reach End.DT6 from a user and net namespace by installing a local SID and injecting an outer packet with Hop-by-Hop and Destination Options headers followed by an SRH and a minimal inner IPv6 packet. The outer extension headers leave a large nhoff in IP6CB. After decapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the inner packet and reads beyond the skb head. KASAN reports: BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu ip6_protocol_deliver_rcu+0x1118/0x1450 ip6_input_finish+0x11b/0x240 seg6_local_input_core+0xed/0x2e0 lwtunnel_input+0x1e9/0x4e0 ipv6_rthdr_rcv+0x525f/0x6c50 ip6_protocol_deliver_rcu+0xcb7/0x1450 Before clearing IP6CB for an inner IPv6 packet, save its incoming interface index and L3 slave state. Restore both after the clear and set nhoff to the inner IPv6 base-header nexthdr field. Use IP6CB(skb)->iif rather than skb->skb_iif because VRF processing can replace skb_iif with the L3 master while IP6CB keeps the receiving interface. Preserve IP6SKB_L3SLAVE for the same reason.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.006260000 probability, percentile 0.481060000 (date 2026-09-14)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 d1f0d353358987ca87f21d8956e2d2854951130d git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 a0e2b0a3718f0cf9fb0ee41710b4a6348a7315c8 git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 9ae92198c24d7dacd4070e2f34f6e1ed3a63061c git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 96c74420ac92930a7e0f21770818544eee4a93d7 git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 2b154e96fcb3f01fd42765c64e0a56820fbc16eb git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 cfa186a0857a0f831dfca67b16bbc40ecfdf3280 git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 c73fb911e02b9a766c950bc9707f3e3a96ffd702 git Not specified
CNA Linux Linux affected d7a669dd2f8ba07a17423f4ad586dfc0379882f7 f967455fb2a5a2079b9eb5823e9ccf359174bf9f git Not specified
CNA Linux Linux affected 4.14 Not specified
CNA Linux Linux unaffected 4.14 semver Not specified
CNA Linux Linux unaffected 5.10.270 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.221 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.188 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/2b154e96fcb3f01fd42765c64e0a56820fbc16eb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9ae92198c24d7dacd4070e2f34f6e1ed3a63061c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c73fb911e02b9a766c950bc9707f3e3a96ffd702 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/96c74420ac92930a7e0f21770818544eee4a93d7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f967455fb2a5a2079b9eb5823e9ccf359174bf9f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a0e2b0a3718f0cf9fb0ee41710b4a6348a7315c8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cfa186a0857a0f831dfca67b16bbc40ecfdf3280 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d1f0d353358987ca87f21d8956e2d2854951130d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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