CVE-2026-63921 | Vulnerability Intelligence

Stored catalog record

Source record retrieved 2026-10-28T10:25:50.378400+00:00. Scheduled imports handle updates; this page does not assert that the provider was queried just now.

Vulnerability overview

In 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.

Patch review priority

Assess exposure and vendor guidance

No higher-priority signal is available in the current stored evidence.

FIRST EPSS: 0.16% · percentile 4.9 · score date 2026-10-27.

EPSS estimates probability of exploitation in the next 30 days. It does not measure your exposure or prove exploitation. The elevated threshold is 10%; CISA KEV takes precedence. About FIRST EPSS ↗

Severity and scoring

CVSS score: 8.8 · HIGH
CVSS version: 3.1
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Weaknesses: CWE-862

CVSS measures technical severity; it does not establish whether this vulnerability is being exploited in your environment.

Known exploitation and remediation

Not listed in the CISA catalog retrieved for this record. This does not establish that exploitation has not occurred.

Verify affected versions and patch availability in the vendor advisory before making changes.

Affected products and versions

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 3.15
Before (exclusive): 5.10.259
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 5.11
Before (exclusive): 5.15.210
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 5.16
Before (exclusive): 6.1.176
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 6.2
Before (exclusive): 6.6.143
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 6.7
Before (exclusive): 6.12.93
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 6.13
Before (exclusive): 6.18.35
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
From (inclusive): 6.19
Before (exclusive): 7.0.12
cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:*

These are NVD CPE applicability entries. Some products depend on configuration conditions; consult the official record to confirm applicability.

Advisories and references

Explore official sources

Read the official NVD record ↗

Explore the CISA catalog ↗

Back to CVE intelligence