CVE-2026-98271 (GCVE-0-2026-98271)
Vulnerability from cvelistv5
Published
2026-10-06 08:45
Modified
2026-10-19 09:16
Severity ?
Summary
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
References
Impacted products
Vendor Product Version
Linux Linux Version: 6fa01ccd883021105e9f8af7d04b9f156fa3494a
Version: 6fa01ccd883021105e9f8af7d04b9f156fa3494a
Version: 6fa01ccd883021105e9f8af7d04b9f156fa3494a
Version: 6fa01ccd883021105e9f8af7d04b9f156fa3494a
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/skbuff.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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            },
            {
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/core/skbuff.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.7"
            },
            {
              "lessThan": "4.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.54",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.112",
                  "versionStartIncluding": "4.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.54",
                  "versionStartIncluding": "4.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.8",
                  "versionStartIncluding": "4.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "4.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:16:41.976Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/75e4a3e62531738c124c8555a626426fca29d392"
        },
        {
          "url": "https://git.kernel.org/stable/c/bff8a8e53a6d290bc2777bde36d3cb6317b8463d"
        },
        {
          "url": "https://git.kernel.org/stable/c/12929ed66a5166177ef5f06d3da81e4f99993e90"
        },
        {
          "url": "https://git.kernel.org/stable/c/a5117e1eccac6ee3bd4aed7cacf8ebcb6b3eb309"
        }
      ],
      "title": "net: skbuff: do not leave stale header offsets after pskb_carve()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98271",
    "datePublished": "2026-10-06T08:45:33.298Z",
    "dateReserved": "2026-09-25T10:25:14.333Z",
    "dateUpdated": "2026-10-19T09:16:41.976Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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