FKIE_CVE-2026-98570

Vulnerability from fkie_nvd - Published: 2026-10-18 16:17 - Updated: 2026-10-19 10:19
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: keep room for the mac header in dst_dev_overhead() The seg6, ioam6 and rpl lwtunnels size their skb_cow_head() request as the length they are about to push plus dst_dev_overhead(), then push the new headers and rebuild the mac header below them with skb_mac_header_rebuild(). That rebuild needs skb->mac_len of headroom, but dst_dev_overhead() leaves LL_RESERVED_SPACE() of the egress device, 16 bytes for plain Ethernet. Where the mac header is longer than that, as it is on ingress through a VLAN device with reorder_hdr off, the rebuild runs out of room: skb_set_mac_header(skb, -skb->mac_len) computes a negative offset, stores it unchecked in the u16 skb->mac_header, and the memmove that follows writes skb->mac_len bytes about 64 KB past skb->head. Forwarding plain ping6 traffic through such a device reproduces it on all five seg6 encapsulation modes and on the rpl and ioam6 inline paths; skb->mac_header comes back as 65534 on a 704-byte head. Return the larger of the two. The helper already returns skb->mac_len when it has no dst, so this only makes the other branch agree, and it covers every caller rather than each call site in turn.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/36c07127924f11fc5741a780abcaaf808fe9ef13
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/87cd6b717e4069dca34e0866e57eaeb44d3b173e
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/dst.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "36c07127924f11fc5741a780abcaaf808fe9ef13",
              "status": "affected",
              "version": "dce525185bc92864e5a318040285ee070563fe34",
              "versionType": "git"
            },
            {
              "lessThan": "87cd6b717e4069dca34e0866e57eaeb44d3b173e",
              "status": "affected",
              "version": "dce525185bc92864e5a318040285ee070563fe34",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "8471e228448a818e4c27cab4b681b2e758e46cf5",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "c432cd18a07b623651ed15ea167bd303467004cc",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "634710a372ba65bee667c2f6e58a97658c639eab",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "c447c5a9c47bb4858ab12bf90879fe595d2b7f46",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ab9de9c48316d2622d3bf353916b99971570e2c9",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "2fcc9f3798ef82399564d247458e69abd10e683b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "371d8dc298b4f59e99b4564ac5d906fce0932c69",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "b26f015dfb07b6be12d005a0ed0c5c43b7bedbf3",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "c0b11dc50590e10590b39dcda79835cd32f49d00",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "4c12c3c8abd8b888945d31e7bdbb0d8b73032fc5",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "25d8e065c7972dc98fd7a4cac322d5367eaede88",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "4a855c5aec41bf84922224ab7a74e088776e3ac4",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "a9f0407414e16176fdbbbd298c9e18d6dfdf96bc",
              "versionType": "git"
            },
            {
              "lessThan": "6.13",
              "status": "affected",
              "version": "6.12.16",
              "versionType": "semver"
            },
            {
              "lessThan": "6.14",
              "status": "affected",
              "version": "6.13.4",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.179",
              "versionType": "semver"
            },
            {
              "lessThan": "6.2",
              "status": "affected",
              "version": "6.1.130",
              "versionType": "semver"
            },
            {
              "lessThan": "6.7",
              "status": "affected",
              "version": "6.6.81",
              "versionType": "semver"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.235",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "include/net/dst.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.14"
            },
            {
              "lessThan": "6.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: keep room for the mac header in dst_dev_overhead()\n\nThe seg6, ioam6 and rpl lwtunnels size their skb_cow_head() request as\nthe length they are about to push plus dst_dev_overhead(), then push the\nnew headers and rebuild the mac header below them with\nskb_mac_header_rebuild().  That rebuild needs skb-\u003emac_len of headroom,\nbut dst_dev_overhead() leaves LL_RESERVED_SPACE() of the egress device,\n16 bytes for plain Ethernet.\n\nWhere the mac header is longer than that, as it is on ingress through a\nVLAN device with reorder_hdr off, the rebuild runs out of room:\nskb_set_mac_header(skb, -skb-\u003emac_len) computes a negative offset,\nstores it unchecked in the u16 skb-\u003emac_header, and the memmove that\nfollows writes skb-\u003emac_len bytes about 64 KB past skb-\u003ehead.\nForwarding plain ping6 traffic through such a device reproduces it on\nall five seg6 encapsulation modes and on the rpl and ioam6 inline paths;\nskb-\u003emac_header comes back as 65534 on a 704-byte head.\n\nReturn the larger of the two.  The helper already returns skb-\u003emac_len\nwhen it has no dst, so this only makes the other branch agree, and it\ncovers every caller rather than each call site in turn."
    }
  ],
  "id": "CVE-2026-98570",
  "lastModified": "2026-10-19T10:19:15.053",
  "metrics": {},
  "published": "2026-10-18T16:17:09.233",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/36c07127924f11fc5741a780abcaaf808fe9ef13"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/87cd6b717e4069dca34e0866e57eaeb44d3b173e"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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