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Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100569)

high Nessus Plugin ID 336455

Synopsis

The Unity Linux host is missing one or more security updates.

Description

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-100569 advisory.

 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.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected kernel package.

See Also

https://nvd.nist.gov/vuln/detail/CVE-2026-63921

http://www.nessus.org/u?21898cc0

http://www.nessus.org/u?3ff4c65e

Plugin Details

Severity: High

ID: 336455

File Name: unity_linux_UTSA-2026-100569.nasl

Version: 1.1

Type: Local

Published: 8/17/2026

Updated: 8/17/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 93.84

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2026-63921

CVSS v3

Risk Factor: High

Base Score: 8.8

Temporal Score: 7.7

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 8/13/2026

Vulnerability Publication Date: 7/7/2026

Reference Information

CVE: CVE-2026-63921