In the Linux kernel, the following vulnerability has been resolved:
tcp: reject net_iov in zerocopy receive mapping hints
After copying a readable prefix, receive_fallback_to_copy() asks
tcp_zerocopy_set_hint_for_skb() where page mapping can resume. If the
next skb is unreadable, find_next_mappable_frag() passes its net_iov
fragment to can_map_frag().
skb_frag_page() returns NULL for a net_iov, but can_map_frag()
dereferences it in PageCompound(). A v7.2 KASAN run on a connected TCP
socket with 64 readable bytes followed by a 4096-byte NET_IOV_DMABUF
fragment reported:
BUG: KASAN: null-ptr-deref in can_map_frag
tcp_zerocopy_receive -> can_map_frag
Kernel panic - not syncing: KASAN: panic_on_warn set
The diagnostic inserted the net_iov directly because the test host has
no devmem-capable NIC. Hardware end-to-end reachability remains untested
and requires CONFIG_NET_DEVMEM plus a supported DMA-buf-bound RX queue.
Reject all net_iov fragments before skb_frag_page(). This covers both
DMABUF and IOURING net_iov types while leaving page-backed checks
unchanged. With the guard, the same queue copied the readable prefix,
returned a 4096-byte skip hint, and completed without a fault.
tcp: reject net_iov in zerocopy receive mapping hints
After copying a readable prefix, receive_fallback_to_copy() asks
tcp_zerocopy_set_hint_for_skb() where page mapping can resume. If the
next skb is unreadable, find_next_mappable_frag() passes its net_iov
fragment to can_map_frag().
skb_frag_page() returns NULL for a net_iov, but can_map_frag()
dereferences it in PageCompound(). A v7.2 KASAN run on a connected TCP
socket with 64 readable bytes followed by a 4096-byte NET_IOV_DMABUF
fragment reported:
BUG: KASAN: null-ptr-deref in can_map_frag
tcp_zerocopy_receive -> can_map_frag
Kernel panic - not syncing: KASAN: panic_on_warn set
The diagnostic inserted the net_iov directly because the test host has
no devmem-capable NIC. Hardware end-to-end reachability remains untested
and requires CONFIG_NET_DEVMEM plus a supported DMA-buf-bound RX queue.
Reject all net_iov fragments before skb_frag_page(). This covers both
DMABUF and IOURING net_iov types while leaving page-backed checks
unchanged. With the guard, the same queue copied the readable prefix,
returned a 4096-byte skip hint, and completed without a fault.
Metrics
Affected Vendors & Products
Advisories
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 23 Oct 2026 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: tcp: reject net_iov in zerocopy receive mapping hints After copying a readable prefix, receive_fallback_to_copy() asks tcp_zerocopy_set_hint_for_skb() where page mapping can resume. If the next skb is unreadable, find_next_mappable_frag() passes its net_iov fragment to can_map_frag(). skb_frag_page() returns NULL for a net_iov, but can_map_frag() dereferences it in PageCompound(). A v7.2 KASAN run on a connected TCP socket with 64 readable bytes followed by a 4096-byte NET_IOV_DMABUF fragment reported: BUG: KASAN: null-ptr-deref in can_map_frag tcp_zerocopy_receive -> can_map_frag Kernel panic - not syncing: KASAN: panic_on_warn set The diagnostic inserted the net_iov directly because the test host has no devmem-capable NIC. Hardware end-to-end reachability remains untested and requires CONFIG_NET_DEVMEM plus a supported DMA-buf-bound RX queue. Reject all net_iov fragments before skb_frag_page(). This covers both DMABUF and IOURING net_iov types while leaving page-backed checks unchanged. With the guard, the same queue copied the readable prefix, returned a 4096-byte skip hint, and completed without a fault. | |
| Title | tcp: reject net_iov in zerocopy receive mapping hints | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-23T12:22:39.451Z
Reserved: 2026-09-25T10:25:14.388Z
Link: CVE-2026-99055
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-23T13:17:29.140
Modified: 2026-10-23T13:17:29.140
Link: CVE-2026-99055
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.