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CVE-2026-72451
xfrm: Fix xfrm state cache insertion race
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/xfrm. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72451 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 | 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
The xfrm input state cache insertion code checks the validity of the state before acquiring the global xfrm_state_lock. Thus it's possible for someone else to kill the state after it passed the validity check, and then the insertion will add the dead state to the cache. Fix this by moving the validity check inside the lock. This entire function is called on the input path, where BH must be off (e.g., the caller of this function xfrm_input acquires its spinlocks without disabling BH). So there is no need to disable BH here or take the RCU read lock. Remove both and replace them with an assertion that trips if BH is accidentally enabled on some future calling path.
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_state.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/xfrm/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w 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 switch
- CONFIG_XFRM
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
- 0.67%, higher than 51.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.12.13 | 6.12.97 | 6dab4dec9a49 |
| 6.13 | 6.18.40 | a1a3360a0c44 |
| 6.13 | 7.1.5 | 041859fd55c8 |
| 6.13 | 7.2 | ddd3d0132920 |
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
- The flaw is hit on the inbound IPsec path (xfrm_input/xfrm_input_state_lookup) when processing remote ESP/AH or UDP-encap ESP packets on internet-facing VPN gateways, cloud IPsec endpoints, and other systems terminating IPsec from the network.
- AC:LAttack complexity, low
- An attacker can drive both sides of the race by flooding inbound IPsec packets while concurrently deleting or expiring the same SA (netlink XFRM_MSG_DELSA with CAP_NET_ADMIN in a user namespace, or kernel hard-expiry timers during rekey).
- PR:NPrivileges required, none
- Remote exploitation needs no privileges on the victim: crafted ESP/AH packets trigger the lookup while the kernel or IKE stack concurrently tears down the matching SA via timers, rekey, or administrative SA deletion.
- UI:NUser interaction, none
- No victim user interaction is required beyond normal IPsec operation on hosts that already receive and decrypt IPsec traffic; exploitation is driven entirely by attacker-sent packets and concurrent SA teardown.
- S:UScope, unchanged
- The bug corrupts kernel memory on the IPsec endpoint itself and enables standard kernel privilege escalation; it does not cross VM, container, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- A deleted xfrm_state can be inserted into the per-CPU input cache and later referenced after free, creating a use-after-free that enables heap spraying and arbitrary kernel memory disclosure via stale structure fields.
- I:HIntegrity impact, high
- Subsequent cache hits dereference the freed xfrm_state (spin_lock, type->input function pointers, crypto context pointers), providing controllable heap corruption primitives suitable for arbitrary kernel code execution.
- A:HAvailability impact, high
- Dereferencing freed xfrm_state objects during input processing can cause kernel oops/panic, and successful exploitation can crash or hang the system; use-after-free on the softirq receive path inherently threatens availability.