CVE-2026-98271: Linux kernel · net: skbuff: do not leave stale header offsets after pskb_carve()

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: do not leave stale header offsets after pskb_carve() pskb_carve_inside_header() and pskb_carve_inside_nonlinear() remove the first bytes of a packet and reallocate skb->head. All the headers that were present before the operation are gone, but both functions call skb_headers_offset_update(skb, 0), which is a no-op : skb->mac_header, skb->network_header, skb->transport_header and skb->csum_start keep their old values and now describe bytes which are no longer there. Both helpers size the new head from the old skb_end_offset(), so the stale offsets still land inside the new allocation. They point past skb_tail_pointer() though, to bytes that were never initialized. pskb_carve_inside_nonlinear() is the worst case, because it leaves a zombie skb with an empty linear part (skb->data == skb_tail_pointer(skb), skb_headlen(skb) == 0), while skb_mac_header_was_set() is still true and skb->mac_header is way ahead of skb->data. The only user of pskb_extract() is rds_tcp_data_recv(), and the carved skb is queued on tinc->ti_skb_list. When the RDS incoming message is released, rds_tcp_inc_free() calls skb_queue_purge(), which frees the skbs with SKB_DROP_REASON_QUEUE_PURGE. This is visible from drop_monitor, which then tries to pull back to the (bogus) mac header : skbuff: __skb_pull(len=234) skb len=6968 data_len=6968 headroom=0 headlen=0 tailroom=0 end-tail=384 mac=(234,14) mac_len=14 net=(248,40) trans=288 shinfo(txflags=0 nr_frags=1 gso(size=1428 type=16 segs=5)) csum(0x100120 start=288 offset=16 ip_summed=3 complete_sw=0 valid=1 level=0) hash(0x7b446c6c sw=0 l4=1) proto=0x86dd pkttype=0 iif=60 kernel BUG at ./include/linux/skbuff.h:2847! Add skb_carve_reset_headers() to mark the mac and transport headers as not set, reset the network header, clear skb->mac_len, and drop a now meaningless CHECKSUM_PARTIAL (csum_start no longer describes anything). Invalidate the inner offsets as well. Unlike mac_header and transport_header they have no "unset" sentinel, so a leftover non-zero value still looks like a real header. Zero skb->inner_mac_header, skb->inner_network_header, skb->inner_transport_header, skb->inner_protocol and skb->encapsulation, so that all the header state is invalidated in one place. v2: fixed an inaccurate changelog. The stale offsets stay inside the new skb->head, which is never smaller than the old one, they simply point past skb_tail_pointer() to bytes that are gone. Thanks to Xuanqiang Luo for insisting on this. Also invalidate the inner header state, as suggested by the netdev AI review : https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260911114922.621937-1-edumazet%40google.com

• ubuntu.com/security/CVE-2026-98271 (opens in a new tab)
• cve.org/CVERecord?id=CVE-2026-98271 (opens in a new tab)
• git.kernel.org/linus/a5117e1eccac6ee3bd4aed7cacf8ebcb6b3eb309 (opens in a new tab)
• git.kernel.org/stable/c/12929ed66a5166177ef5f06d3da81e4f99993e90 (opens in a new tab)
• git.kernel.org/stable/c/75e4a3e62531738c124c8555a626426fca29d392 (opens in a new tab)
• git.kernel.org/stable/c/a5117e1eccac6ee3bd4aed7cacf8ebcb6b3eb309 (opens in a new tab)
• git.kernel.org/stable/c/bff8a8e53a6d290bc2777bde36d3cb6317b8463d (opens in a new tab)

• CVE-2026-99076: Linux kernel · ipv6: udp: Create exceptions before socket matchingMediumVulnerability2026-10-26
• CVE-2026-99045: Linux kernel · ibmveth: h_free logical LAN on open-fail after registerMediumVulnerability2026-10-26
• CVE-2026-99040: Linux kernel · KEYS: Fix add_key() race with keyring restrictionMediumVulnerability2026-10-26
• CVE-2026-99037: Linux kernel · dm-crypt: reject the lmk IV mode with AEAD ciphersMediumVulnerability2026-10-26
• CVE-2026-99024: Linux kernel · optee: register TEE devices only once fully initializedMediumVulnerability2026-10-26