FKIE_CVE-2026-89563

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-10-19 09:17
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit() ip6_tnl_xmit() may need to expand headroom before it can push the outer IPv6 and optional encap headers. It currently does that with skb_realloc_headroom(), copies skb->sk ownership, consumes the original skb, and then continues processing with the replacement skb kept only in its local variable. That is safe only if the helper cannot fail afterwards. But this helper still has post-reallocation error exits. collect_md tunnels reject non-NONE encap after the replacement, and ip6_tnl_encap() can also fail later. In those cases the helper returns an error to its callers while the caller still only has the original skb pointer. Both ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on error, so they can end up freeing an skb that ip6_tnl_xmit() already consumed. Use skb_cow_head() instead. It provides the required headroom and writability without privately replacing the caller-owned skb, so later error returns cannot leave callers with a stale pointer. The Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING and already call skb_cow_head() before entering ip6_tnl_xmit(). They do not rely on the removed skb_shared() reallocation. This also makes the IPv6 tunnel path consistent with ip_tunnel_xmit().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_tunnel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6e8eff8ed13b14708bc39f170144eacde494aac6",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "dc1a319a4815c074914e2812e0e9cd0164ca682b",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "629d5557e635cdbc109a14ed913ba5a540e3f79a",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "defa0adeff132cc90ed66915b9a104d9393e1e54",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "37df5bc6b5ccad88c2faa0f5466f150178882b74",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "b36dfd6e8cff00cea81c11cc0af88d1564763461",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            },
            {
              "lessThan": "87f21b59ddc618eff9670c174842964ad65fdade",
              "status": "affected",
              "version": "058214a4d1dfefed9f01a277fadd3590acb5f990",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_tunnel.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": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "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\nip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()\n\nip6_tnl_xmit() may need to expand headroom before it can push the\nouter IPv6 and optional encap headers. It currently does that with\nskb_realloc_headroom(), copies skb-\u003esk ownership, consumes the original\nskb, and then continues processing with the replacement skb kept only in\nits local variable.\n\nThat is safe only if the helper cannot fail afterwards. But this helper\nstill has post-reallocation error exits. collect_md tunnels reject\nnon-NONE encap after the replacement, and ip6_tnl_encap() can also fail\nlater. In those cases the helper returns an error to its callers while\nthe caller still only has the original skb pointer.\n\nBoth ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on\nerror, so they can end up freeing an skb that ip6_tnl_xmit() already\nconsumed.\n\nUse skb_cow_head() instead. It provides the required headroom and\nwritability without privately replacing the caller-owned skb, so later\nerror returns cannot leave callers with a stale pointer.\n\nThe Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING\nand already call skb_cow_head() before entering ip6_tnl_xmit(). They do\nnot rely on the removed skb_shared() reallocation. This also makes the\nIPv6 tunnel path consistent with ip_tunnel_xmit()."
    }
  ],
  "id": "CVE-2026-89563",
  "lastModified": "2026-10-19T09:17:52.040",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-89563",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-16T19:24:12.096672Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-11T20:19:40.193",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.