CVE-2026-64566 xfrm: iptfs: propagate SKBFL_SHARED_FRAG in iptfs_skb_add_frags()
A missing flag propagation in the Linux kernel's IPTFS module allows memory corruption and potential code execution during ESP decryption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64566?
CVE-2026-64566 is a critical memory corruption vulnerability in Linux, published on 5 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
xfrm: iptfs: propagate SKBFL_SHARED_FRAG in iptfs_skb_add_frags()
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.
Which versions are affected by CVE-2026-64566?
How do I fix CVE-2026-64566?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-64566 being exploited?
There is no known exploitation of CVE-2026-64566 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-64566, DEBIAN-CVE-2026-64566, GHSA-wr7x-h83j-8fqg, UBUNTU-CVE-2026-64566.