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CVE-2026-72463
xfrm: Fix dev use-after-free in xfrm async resumption
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72463 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixedDSA-6568-1 · 2026-10-16 · text | 6.12.113-1 | Update the kernel and reboot. DSA-6568-1 shipped the fix on 2026-10-16, in 6.12.113-1. 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
xfrm async resumption hold skb->dev refcnt until after transport_finish. However, xfrm_rcv_cb may modify skb->dev to tunnel dev without taking device reference, such as vti_rcv_cb. The subsequent async resumption will decrement the tunnel device's reference count, which lead to uaf of tunnel dev and refcnt leak of orig dev as below: unregister_netdevice: waiting for vti1 to become free. Usage count = -2 Stash the original skb->dev to fix refcnt imbalance. The new skb->dev set by xfrm_rcv_cb can race with device teardown. Extend rcu protection over xfrm_rcv_cb and transport_finish to prevent races.
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/ipv4/xfrm4_input.c
net/ipv6/xfrm6_input.c
net/xfrm/xfrm_input.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/ipv4/xfrm* · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_INET|CONFIG_XFRM' /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.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switches
- CONFIG_INET, CONFIG_XFRM
- 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
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.44%, higher than 37.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/ipv4
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.12.94 | 6.12.112 | fed4d3195a31 |
| 6.18.23 | 6.18.54 | 1acd93259b6b |
| 7.0 | 7.1.5 | 63a300151999 |
| 7.0 | 7.2 | 8045c0df98d4 |
| 6.19.13 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6568-1 | 2026-10-16 | trixie 6.12.113-1 | 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:NAttack vector, network
- Reachable from the network receive path: remote ESP/AH (or UDP-encapsulated IPsec) packets hit ip_rcv → xfrm4/xfrm6 protocol handlers → vti/xfrmi input → xfrm_input() → async crypto resume, on Internet-facing IPsec/VTI/xfrmi VPN gateways and cloud endpoints.
- AC:LAttack complexity, low
- Once async decryption resumes (encap_type=-1), vti_rcv_cb/xfrmi_rcv_cb retarget skb->dev and the stale dev_put is deterministic; the attacker controls packet rate/volume to drive -EINPROGRESS and can race netdev teardown, so no uncontrollable victim-only conditions apply.
- PR:NPrivileges required, none
- No local account, shell, or capability on the victim is required—only network-delivered IPsec traffic accepted by a pre-configured VTI/xfrmi gateway (e.g., VPN peer, site-to-site endpoint); administrative IPsec setup is deployment state, not attacker privilege on the host.
- UI:NUser interaction, none
- Exploitation is fully automated by sending IPsec packets; no victim interaction such as mounting filesystems, opening files, or clicking links is needed.
- S:UScope, unchanged
- Impact is kernel net_device refcount corruption/UAF within the host kernel security authority; it does not cross VM, IOMMU, or sandbox boundaries (standard kernel privilege escalation, not escape).
- C:HConfidentiality impact, high
- Use-after-free of a net_device after refcount underflow (e.g., usage count=-2) exposes freed netdev/slab memory; per kernel UAF guidance this provides a high-impact arbitrary-read primitive via heap grooming.
- I:HIntegrity impact, high
- Corrupting freed net_device structures and reference counts is classic heap UAF that can be shaped into arbitrary kernel writes and control-flow hijack for code execution, per kernel memory-corruption guidance.
- A:HAvailability impact, high
- Refcount imbalance causes unregister_netdevice to hang (usage count=-2), kernel oops/panic during tunnel teardown, and reliable denial of service on IPsec gateways even before full exploitation.