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CVE-2026-72055
net: ip6_vti: require CAP_NET_ADMIN in the device netns for changelink
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/ipv6. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72055 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
vti6_changelink() operates on at most two netns, dev_net(dev) and the tunnel link netns t->net. They differ once the device is created in or moved to a netns other than the one the request runs in. The rtnl changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a caller privileged there but not in t->net can rewrite a tunnel that lives in t->net. Gate vti6_changelink() on rtnl_dev_link_net_capable() at its top, before any attribute is parsed.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/ipv6/ip6_vti.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/ipv6/ip6_vti.c · netdev@vger.kernel.org · Maintained
- Kernel module
- ip6_vti
Check it on the machine
grep -w CONFIG_IPV6_VTI /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w ip6_vtiPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_IPV6_VTI
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv6
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.15 | 5.10.261 | f5254e7766b4 |
| 3.15 | 5.15.212 | ef897249dc95 |
| 3.15 | 6.1.178 | f6e8b52a2cb3 |
| 3.15 | 6.6.145 | c64b9ae7eb97 |
| 3.15 | 6.12.97 | b2b61c540571 |
| 3.15 | 6.18.40 | 0b2f9c908f93 |
| 3.15 | 7.1.5 | f97e93ebf2f9 |
| 3.15 | 7.2 | e2ac3b242c37 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The flaw is only reachable through rtnetlink configuration (RTM_NEWLINK changelink via netlink socket), not from remote IPv6/IPsec packets processed by vti6_rcv; kernel guidance classifies netlink/tc paths as Local.
- AC:LAttack complexity, low
- Exploitation is a deterministic attacker-controlled sequence (create vti6, move netns so dev_net(dev) != t->net, issue changelink) with no races, timing dependencies, or uncontrollable victim state once the cross-namespace device exists.
- PR:LPrivileges required, low
- The rtnl entry path requires CAP_NET_ADMIN in dev_net(dev), obtainable by an unprivileged local user inside a user+network namespace (unshare --user --map-root-user --net) without init-namespace root or CAP_NET_ADMIN in t->net.
- UI:NUser interaction, none
- Exploitation is fully programmatic through netlink from the attacker's own process; no victim action such as mounting a filesystem, opening a file, or clicking is required.
- S:CScope, changed
- vti6_changelink mutates live tunnel state and hash tables in t->net while authorization is checked only against dev_net(dev), crossing from the attacker's net/user namespace into another tenant's or the host's network namespace IPsec tunnel configuration.
- C:HConfidentiality impact, high
- Unauthorized changelink can rewrite IFLA_VTI_LOCAL/REMOTE, IKEY/OKEY, and FWMARK to redirect IPv6 IPsec VTI traffic through attacker-controlled endpoints, exposing decrypted tunneled payloads on the receive path.
- I:HIntegrity impact, high
- The attacker can arbitrarily reconfigure live vti6 tunnel endpoints, keys, link binding, and routing metadata in t->net without authorization, enabling traffic redirection and injection across the victim namespace's IPsec VPN paths.
- A:HAvailability impact, high
- Rewriting or invalidating vti6 tunnel endpoints, keys, or link configuration can break production IPsec VPN overlays and dependent services, causing sustained loss of connectivity for workloads in the victim network namespace.