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CVE-2026-64566
xfrm: iptfs: propagate SKBFL_SHARED_FRAG in iptfs_skb_add_frags()
Published 2026-08-05 (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-2026-64566 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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. |
The vulnerability
What the bug is
When iptfs_skb_add_frags() copies frag references from the source frag walk into a new SKB, it increments the page reference count via __skb_frag_ref() but does not propagate SKBFL_SHARED_FRAG to the destination SKB's skb_shinfo->flags. If the source SKB carries shared frags (e.g. from a page-pool backed receive path), the new inner SKB will appear to ESP as having privately owned frags. A subsequent esp_input() call for a nested transport-mode SA then takes the no-COW fast path and decrypts in place, writing over pages that are still referenced by the outer IPTFS SKB. This causes kernel-visible memory corruption and can trigger a panic. All other frag-transfer helpers in the kernel (skb_try_coalesce, skb_gro_receive, __pskb_copy_fclone, skb_shift, skb_segment) correctly propagate SKBFL_SHARED_FRAG; align iptfs_skb_add_frags() with this convention by setting the flag inside the loop immediately after __skb_frag_ref() and nr_frags++, so every exit path that attaches a frag unconditionally propagates SKBFL_SHARED_FRAG.
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_iptfs.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/xfrm/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_XFRM|CONFIG_XFRM_IPTFS' /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 does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_XFRM, CONFIG_XFRM_IPTFS
- 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
- 2026-08-05 (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
- 0.35%, higher than 27.3% 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 |
|---|---|---|
| 6.14 | 6.18.42 | d8aaf06b29f5 |
| 6.14 | 7.1.6 | ffd64e0717ef |
| 6.14 | 7.2 | 430ea57d6daf |
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 on the IPsec IPTFS receive path: inbound ESP packets hit xfrm_input → iptfs_input → iptfs_skb_add_frags, then reinjected inner packets reach nested transport-mode esp_input(); a remote IPTFS/IPsec peer triggers it with network packets.
- AC:LAttack complexity, low
- On a host with IPTFS plus a nested transport-mode SA, the peer fully controls packet sizes and ESP payloads that take the frag-share path and drive in-place decrypt; no race or attacker-uncontrollable memory layout is required.
- PR:NPrivileges required, none
- Exploitation is by a remote IPsec peer sending packets to an already-configured IPTFS endpoint; no local account or capability on the target is required, and SA presence is a deployment precondition rather than an attacker privilege.
- UI:NUser interaction, none
- Packets are processed in softirq/NAPI receive context with no victim action such as mounting, opening a file, or otherwise interacting with the system.
- S:UScope, unchanged
- Corruption is of shared skb/NIC fragment pages within the same kernel security authority; this is not a VM escape, IOMMU bypass, or cross-sandbox boundary crossing.
- C:HConfidentiality impact, high
- Missing SKBFL_SHARED_FRAG lets nested esp_input() overwrite pages still referenced by the outer IPTFS skb and sibling inners, yielding attacker-influenced memory corruption that can be leveraged for information disclosure.
- I:HIntegrity impact, high
- In-place ESP decryption writes attacker-controlled plaintext into pages still held by other skbs, providing a memory-corruption write primitive capable of integrity compromise and control-flow impact.
- A:HAvailability impact, high
- The same shared-page overwrite causes kernel-visible memory corruption and can panic/oops the host, fully denying availability.