Bug 2511410 (CVE-2026-64566)

Summary: CVE-2026-64566 kernel: xfrm: iptfs: propagate SKBFL_SHARED_FRAG in iptfs_skb_add_frags()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's iptfs module, which handles network packet processing. When copying shared packet fragments, a critical flag indicating shared memory is not correctly propagated. This can lead to memory corruption within the kernel, potentially causing the system to crash and resulting in a denial of service.
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Description OSIDB Bzimport 2026-08-05 09:02:12 UTC 
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.
Comment 1 gkamathe 2026-08-06 10:21:19 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026080506-CVE-2026-64566-e654@gregkh/T