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CVE-2026-72052
net: ip6_gre: 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-2026-72052 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
ip6gre_changelink() and ip6erspan_changelink() operate 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 both ops on rtnl_dev_link_net_capable() at their 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_gre.c
- What this is
- NETWORKING [IPv4/IPv6]MAINTAINERS section matched on net/ipv6/ip* · netdev@vger.kernel.org · Maintained
- Kernel module
- ip6_gre
Check it on the machine
grep -w CONFIG_IPV6_GRE /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_grePrints 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_GRE
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 |
|---|---|---|
| 5.5 | 5.10.261 | 129f8939e5af |
| 5.5 | 5.15.212 | e3724dedf577 |
| 5.5 | 6.1.178 | 220162c9fedb |
| 5.5 | 6.6.145 | 1d4d8ee00208 |
| 5.5 | 6.12.97 | 0caa9f348f8b |
| 5.5 | 6.18.40 | 03d8843b143e |
| 5.5 | 7.1.5 | c38c8b0db3c6 |
| 5.5 | 7.2 | f00a50876d28 |
| 4.19.100 | 0 | 0 |
| 5.4.16 | 0 | 0 |
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 bug is reached only via rtnetlink (RTM_NEWLINK changelink) on a local NETLINK_ROUTE socket, not by processing attacker-controlled network packets; kernel guidance classifies rtnetlink control-plane bugs as Local.
- AC:LAttack complexity, low
- With CAP_NET_ADMIN in dev_net(dev) (e.g. via user namespaces), an attacker can move a cross-netns ip6gre device or use an existing one, then issue a single deterministic changelink; no uncontrollable races or rare kernel configs are required.
- PR:LPrivileges required, low
- Exploitation requires CAP_NET_ADMIN in dev_net(dev) to issue RTM_NEWLINK changelink; this capability is available to unprivileged users creating user+network namespaces (unshare -Urn), not only real init-namespace root.
- UI:NUser interaction, none
- No victim interaction is needed once the attacker has a suitable ip6gre/ip6gretap/ip6erspan netdev handle and issues rtnetlink changelink requests to rewrite tunnel parameters.
- S:CScope, changed
- The flaw crosses the network-namespace security boundary: a caller authorized only in dev_net(dev) can modify ip6gre state and routing tables in t->net (another tenant/host namespace), violating netns isolation relied on by containers and Kubernetes.
- C:HConfidentiality impact, high
- changelink can point tunnels/ERSPAN mirroring at attacker-chosen IPv6 endpoints and keys, enabling interception and collection of traffic that other namespaces expect to be privately encapsulated or mirrored only to trusted collectors.
- I:HIntegrity impact, high
- The attacker can arbitrarily rewrite tunnel link parameters (local/remote addresses, keys, encap, fwmark, ERSPAN index) and rehash tunnel state in the victim link netns, redirecting or corrupting network paths outside their authorization.
- A:HAvailability impact, high
- Rewriting or unlinking tunnel entries can immediately break GRE/ERSPAN connectivity depended on for production links, causing sustained network outage or repeated loss of availability without kernel interaction from the victim.