ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().

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Summary

CVECVE-2026-63921
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:10 UTC
Updated2026-07-20 15:16:56 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate(). After patch 1/2 in this series, vti6_update() unlinks and relinks the tunnel through t->net. vti6_siocdevprivate() still uses dev_net(dev) for the collision lookup. For a tunnel moved through IFLA_NET_NS_FD, dev_net(dev) is the new netns, not t->net. SIOCCHGTUNNEL on a migrated tunnel then runs: net = dev_net(dev) /* migrated netns */ t = vti6_locate(net, &p1, false) /* misses target in t->net */ ... t = netdev_priv(dev) vti6_update(t, &p1, false) /* mutates t->net's hash */ A caller in the migrated netns picks params that match a tunnel in the creation netns. The lookup in dev_net(dev) finds nothing. vti6_update() prepends the migrated tunnel at the head of the creation netns hash bucket for those params. Later lookups in the creation netns resolve to the migrated device. xfrm receive delivers the matched packets through a device the caller controls. Reachable from an unprivileged user namespace (unshare --user --map-root-user --net). Cross tenant scope on container hosts. Switch the SIOCCHGTUNNEL path on a non fallback device to use t->net for the lookup. The lookup now matches the netns vti6_update() operates on. Also add ns_capable(self->net->user_ns, CAP_NET_ADMIN) before the lookup. The check at the top of the case is against dev_net(dev)->user_ns, which after migration is the attacker's netns. A caller there can pick params absent from self->net, the lookup returns NULL, t becomes self, and vti6_update() inserts the device into the creation netns hash. The new check requires CAP_NET_ADMIN in the creation netns user_ns too. SIOCADDTUNNEL and SIOCCHGTUNNEL on the fallback device keep dev_net(dev), which equals init_net there.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.002200000 probability, percentile 0.125280000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
3.1CNADECLARED8.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 94ff740a7f9ef5c010784a325dca00cbf228f941 git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 df42ac708acc3399bbb6dc5ca16e0540adda7bbf git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 44d2ff7d2178503b93151140a45dfa2ad49c9906 git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 1acfb7d9c6fc7e209ed7789392697e97e03edd33 git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 d2236348414bdd6558385f35aa7fdc9bf5634011 git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 853f6ea482dfcd3404bbef458ab4d68364eed838 git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 596f6354c96a891e58c04a09cbfb7b0d1ec00dab git Not specified
CNA Linux Linux affected 61220ab349485d911083d0b7990ccd3db6c63297 8b484efd5cb4eeef9021a661e198edc5349dacf6 git Not specified
CNA Linux Linux affected 3.15 Not specified
CNA Linux Linux unaffected 3.15 semver Not specified
CNA Linux Linux unaffected 5.10.259 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/df42ac708acc3399bbb6dc5ca16e0540adda7bbf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8b484efd5cb4eeef9021a661e198edc5349dacf6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1acfb7d9c6fc7e209ed7789392697e97e03edd33 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/94ff740a7f9ef5c010784a325dca00cbf228f941 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/853f6ea482dfcd3404bbef458ab4d68364eed838 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/596f6354c96a891e58c04a09cbfb7b0d1ec00dab 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d2236348414bdd6558385f35aa7fdc9bf5634011 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/44d2ff7d2178503b93151140a45dfa2ad49c9906 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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