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CVE-2026-72450
xfrm: validate selector family and prefixlen during match
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72450 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
syzbot reported a shift-out-of-bounds in xfrm_selector_match() due to AF_UNSPEC selector with large prefixlen (e.g. 128) matched against IPv4 flow (when XFRM_STATE_AF_UNSPEC is set). Fix this by: - Rejecting mismatched families in xfrm_selector_match. - Returning false in addr4_match if prefixlen > 32. - Returning false in addr_match if prefixlen > 128 (prevents overflow).
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.
include/net/xfrm.h
net/xfrm/xfrm_policy.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on include/net/xfrm.h · 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
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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
- include/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10.229 | 5.10.261 | 87a5bbccc7ff |
| 5.15.170 | 5.15.212 | bd7f202cf775 |
| 6.1.115 | 6.1.178 | a3968ad4195d |
| 6.6.59 | 6.6.145 | efa9e3b9f3de |
| 6.12 | 6.12.97 | 78783fefdc8f |
| 6.12 | 6.18.40 | 6d99379c58f7 |
| 6.12 | 7.1.5 | 5a03a2ee17e8 |
| 6.12 | 7.2 | 40f0b1047918 |
| 4.19.323 | 0 | 0 |
| 5.4.285 | 0 | 0 |
| 6.11.6 | 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 armed via NETLINK_XFRM (XFRM_MSG_NEWSA with XFRM_STATE_AF_UNSPEC) in xfrm_user_rcv_msg(), and per kernel CNA guidance xfrm/netlink configuration is Local even though xfrm_selector_match() is later hit from IPv4/IPv6 packet processing in __xfrm_policy_check() and xfrm_state_look_at().
- AC:LAttack complexity, low
- The attacker fully controls the malformed SA selector (AF_UNSPEC with prefixlen up to 255) and can deterministically trigger matching by sending or receiving IPv4/IPv6 traffic through xfrm; no race, victim state, or memory layout outside attacker control is required.
- PR:LPrivileges required, low
- xfrm_user_rcv_msg() requires netlink_net_capable(CAP_NET_ADMIN), evaluated against the socket net namespace user_ns via ns_capable(); an unprivileged local user obtains CAP_NET_ADMIN with unshare -Urn and can install the poisoned SA and matching policy in that namespace.
- UI:NUser interaction, none
- The attacker performs the entire sequence—installing the XFRM SA/policy over netlink and generating matching traffic—with no action required from any other user, administrator, or victim.
- S:UScope, unchanged
- The shift-out-of-bounds and out-of-bounds memcmp reads occur entirely within kernel xfrm selector matching on the same host; no VM escape, IOMMU bypass, or cross-security-authority boundary is crossed.
- C:HConfidentiality impact, high
- addr4_match() performs an undefined left-shift when prefixlen>32 on IPv4 flows, and addr_match() can memcmp() up to (prefixlen>>5)<<2 bytes past 16-byte selector/flow addresses when prefixlen>128 on IPv6, leaking adjacent kernel memory per CNA OOB-read guidance.
- I:HIntegrity impact, high
- C11 undefined-behavior shifts in hot-path packet classification and unchecked prefix comparisons can corrupt mask/offset arithmetic and selector-match control flow, giving attacker-influenced kernel behavior exploitable for integrity compromise per CNA memory-unsafe-operation guidance.
- A:HAvailability impact, high
- syzbot reproduced UBSAN shift-out-of-bounds in xfrm_selector_match(), and undefined shifts plus out-of-bounds reads in the xfrm input/policy-check path can provoke kernel oops/panic (especially with panic_on_warn/KASAN), satisfying CNA guidance that kernel crashes are High availability impact.