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CVE-2026-72136
xfrm: xfrm_interface: require CAP_NET_ADMIN in the device netns for changelink
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/xfrm. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72136 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
xfrmi_changelink() operates on at most two netns, dev_net(dev) and the interface link netns xi->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 xi->net can rewrite an interface that lives in xi->net. Gate xfrmi_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/xfrm/xfrm_interface_core.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/xfrm/ · netdev@vger.kernel.org · Maintained
- Kernel module
- xfrm_interface
Check it on the machine
grep -wE 'CONFIG_XFRM|CONFIG_XFRM_INTERFACE' /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 xfrm_interfacePrints 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 switches
- CONFIG_XFRM, CONFIG_XFRM_INTERFACE
- Reads as
- all on means the file is compiled; any one off means it is not.
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/xfrm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.19 | 5.10.261 | 04c1aa57d084 |
| 4.19 | 5.15.212 | bdfd1c21d90e |
| 4.19 | 6.1.178 | 80ec68bba11f |
| 4.19 | 6.6.145 | e9c90756f10d |
| 4.19 | 6.12.97 | 37b61946d278 |
| 4.19 | 6.18.40 | 8ca2a19a987a |
| 4.19 | 7.1.5 | 3ba2b2ef7d6a |
| 4.19 | 7.2 | 095515d89b19 |
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 a local RTM_NEWLINK changelink over an rtnetlink/netlink socket (rtnl_newlink → rtnl_changelink → xfrmi_changelink); this is a netlink configuration path, not remote packet handling, matching kernel Local guidance.
- AC:LAttack complexity, low
- Once a cross-namespace xfrmi exists (dev_net(dev) ≠ xi->net via IFLA_LINK_NETNSID creation or netns migration), bypassing the missing check is one deterministic changelink with attacker-chosen IFLA_XFRM_IF_ID; no race, timing, or layout dependency.
- PR:LPrivileges required, low
- rtnl_link_get_net_capable() only requires CAP_NET_ADMIN in dev_net(dev), obtainable by an unprivileged user via user+network namespaces (unshare -Urn / map-root-user); CAP_NET_ADMIN in the sticky link netns xi->net is not required.
- UI:NUser interaction, none
- The attack is fully programmatic from the attacker's own process through netlink; no victim action such as mounting a filesystem, opening a file, or clicking is required.
- S:CScope, changed
- Privilege is checked against dev_net(dev) while xfrmi_changelink/xfrmi_update mutate live xfrm interface state in xi->net (hash unlink/relink, if_id binding), crossing from the attacker's net/user namespace into another tenant's or the host network namespace.
- C:HConfidentiality impact, high
- Changing IFLA_XFRM_IF_ID in xi->net retargets xfrmi_lookup/xfrm_lookup_with_ifid so host IPsec SAs can deliver decrypted VPN cleartext to the attacker-controlled netdev in dev_net(dev), exposing confidential tunneled traffic.
- I:HIntegrity impact, high
- Unauthorized changelink rewrites live xfrm interface parameters and xi->net registration, enabling redirection or injection of IPsec encapsulation/decapsulation paths on Internet-facing VPN gateways and cloud IPsec endpoints.
- A:HAvailability impact, high
- xfrmi_update() runs synchronize_net() and netdev_state_change(); breaking or rebinding if_id mapping disrupts production IPsec/VTI/xfrmi VPN paths, causing sustained loss of encrypted tunnel connectivity.