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CVE-2026-68142
geneve: require CAP_NET_ADMIN in the device netns for changelink
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68142 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
A tunnel changelink() operates on at most two netns, dev_net(dev) and the sticky underlay netns geneve->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 geneve->net can rewrite a geneve device whose underlay lives in geneve->net. geneve_changelink() applies the new configuration against geneve->net: geneve_link_config() and the geneve_quiesce()/geneve_unquiesce() pair reopen the underlay sockets in that netns (geneve_sock_add() uses geneve->net), so the same reasoning as the tunnel changelink series applies here. Gate geneve_changelink() with rtnl_dev_link_net_capable(), at the top of the op before any attribute is parsed, matching ipgre_changelink() and the rest of the "require CAP_NET_ADMIN in the device netns for changelink" series. Found by 0sec automated security-research tooling (https://0sec.ai).
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.
drivers/net/geneve.c
- What this is
- NETWORKING DRIVERSMAINTAINERS section matched on drivers/net/ · netdev@vger.kernel.org · Maintained
- Kernel module
- geneve
Check it on the machine
grep -w CONFIG_GENEVE /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 genevePrints 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, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_GENEVE
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
- 2026-08-10 (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
- 0.14%, higher than 2.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.14 | 5.10.265 | a5522963c57f |
| 4.14 | 5.15.216 | 278c6a31ee27 |
| 4.14 | 6.1.183 | 11a7d989d001 |
| 4.14 | 6.6.148 | 2abdacc927c9 |
| 4.14 | 6.12.101 | 9de5518fc1fa |
| 4.14 | 6.18.42 | f8c498585d2a |
| 4.14 | 7.1.6 | 95f45e20f1b2 |
| 4.14 | 7.2 | 8efb8f8bbb35 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | tracker |
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
- Exploitation requires issuing RTM_NEWLINK changelink over a local rtnetlink socket; geneve_changelink is only reachable from the rtnl configuration path, not from received GENEVE/UDP network packets.
- AC:LAttack complexity, low
- Once a geneve device exists with geneve->net differing from dev_net(dev) (via IFLA_NET_NS_FD migration or IFLA_LINK_NETNSID newlink), a single deterministic netlink changelink bypasses the missing check with no race or memory-layout dependency.
- 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 via unshare --user --map-root-user --net; no CAP_NET_ADMIN in the sticky underlay netns geneve->net is needed.
- UI:NUser interaction, none
- The attack 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
- geneve_changelink applies geneve_link_config() and geneve_quiesce()/geneve_unquiesce() (reopening underlay sockets via geneve_sock_add() in geneve->net) while authorization is checked only against dev_net(dev), crossing into another tenant's or the host's network namespace.
- C:HConfidentiality impact, high
- An attacker can set IFLA_GENEVE_REMOTE/REMOTE6 to redirect encapsulated overlay traffic to an attacker-controlled endpoint and read tunneled payloads from the victim underlay netns.
- I:HIntegrity impact, high
- Unauthorized changelink mutates live tunnel remote endpoint, TTL/TOS/DF/label, and MTU in geneve->net, enabling redirection and injection of overlay traffic without authorization in that namespace.
- A:HAvailability impact, high
- geneve_quiesce() drops in-flight tunnel traffic and rewriting the remote endpoint or MTU breaks production GENEVE overlays (Kubernetes/OVN/cloud SDN), causing sustained loss of connectivity for dependent services.