{"id":"AZL-106374","summary":"CVE-2026-98271 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skbuff: do not leave stale header offsets after pskb_carve()\n\npskb_carve_inside_header() and pskb_carve_inside_nonlinear() remove\nthe first bytes of a packet and reallocate skb-\u003ehead.\n\nAll the headers that were present before the operation are gone,\nbut both functions call skb_headers_offset_update(skb, 0), which\nis a no-op : skb-\u003emac_header, skb-\u003enetwork_header,\nskb-\u003etransport_header and skb-\u003ecsum_start keep their old values and\nnow describe bytes which are no longer there.\n\nBoth helpers size the new head from the old skb_end_offset(), so the\nstale offsets still land inside the new allocation. They point past\nskb_tail_pointer() though, to bytes that were never initialized.\n\npskb_carve_inside_nonlinear() is the worst case, because it leaves a\nzombie skb with an empty linear part (skb-\u003edata ==\nskb_tail_pointer(skb), skb_headlen(skb) == 0), while\nskb_mac_header_was_set() is still true and skb-\u003emac_header is way\nahead of skb-\u003edata.\n\nThe only user of pskb_extract() is rds_tcp_data_recv(), and the\ncarved skb is queued on tinc-\u003eti_skb_list. When the RDS incoming\nmessage is released, rds_tcp_inc_free() calls skb_queue_purge(),\nwhich frees the skbs with SKB_DROP_REASON_QUEUE_PURGE. This is\nvisible from drop_monitor, which then tries to pull back to the\n(bogus) mac header :\n\nskbuff: __skb_pull(len=234)\nskb len=6968 data_len=6968 headroom=0 headlen=0 tailroom=0\nend-tail=384 mac=(234,14) mac_len=14 net=(248,40) trans=288\nshinfo(txflags=0 nr_frags=1 gso(size=1428 type=16 segs=5))\ncsum(0x100120 start=288 offset=16 ip_summed=3 complete_sw=0 valid=1 level=0)\nhash(0x7b446c6c sw=0 l4=1) proto=0x86dd pkttype=0 iif=60\nkernel BUG at ./include/linux/skbuff.h:2847!\n\nAdd skb_carve_reset_headers() to mark the mac and transport headers\nas not set, reset the network header, clear skb-\u003emac_len, and drop\na now meaningless CHECKSUM_PARTIAL (csum_start no longer describes\nanything).\n\nInvalidate the inner offsets as well. Unlike mac_header and\ntransport_header they have no \"unset\" sentinel, so a leftover\nnon-zero value still looks like a real header. Zero\nskb-\u003einner_mac_header, skb-\u003einner_network_header,\nskb-\u003einner_transport_header, skb-\u003einner_protocol and\nskb-\u003eencapsulation, so that all the header state is invalidated in\none place.\n\nv2: fixed an inaccurate changelog. The stale offsets stay inside the\n    new skb-\u003ehead, which is never smaller than the old one, they\n    simply point past skb_tail_pointer() to bytes that are gone.\n    Thanks to Xuanqiang Luo for insisting on this.\n    Also invalidate the inner header state, as suggested by the\n    netdev AI review :\n    https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260911114922.621937-1-edumazet%40google.com","modified":"2026-10-08T05:35:32Z","published":"2026-10-06T09:18:16Z","upstream":["CVE-2026-98271"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98271"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-106374.json"}}],"schema_version":"1.9.0"}