CVE-2026-99055 is a vulnerability in Linux Kernel
Published on October 23, 2026
tcp: reject net_iov in zerocopy receive mapping hints
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.
Products Associated with CVE-2026-99055
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Affected Versions
Linux:- Version 9f6b619edf2e85746f261b42ae8f818a59d126f7 and below 563d3564513496b9ce3b3ba7a5154427554d0f06 is affected.
- Version 9f6b619edf2e85746f261b42ae8f818a59d126f7 and below 1c7463ac0e99cc91c4eecc1b69a740ef1a619932 is affected.
- Version 9f6b619edf2e85746f261b42ae8f818a59d126f7 and below 3aa6f536a95eb0617c313ae2eb76fdfa85331f85 is affected.
- Version 9f6b619edf2e85746f261b42ae8f818a59d126f7 and below 8b1f0af1fd5fd113432233ed8a3862ee7c30a84f is affected.
- Version 6.12 is affected.
- Before 6.12 is unaffected.
- Version 6.12.113, <= 6.12.* is unaffected.
- Version 6.18.57, <= 6.18.* is unaffected.
- Version 7.2.11, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.