CVE-2026-63993 (GCVE-0-2026-63993)
Vulnerability from cvelistv5
Published
2026-07-19 14:56
Modified
2026-08-05 12:37
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.
References
Impacted products
Vendor Product Version
Linux Linux Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
Version: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/vxlan/vxlan_core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "5.9"
            },
            {
              "lessThan": "5.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.259",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.210",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
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            },
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              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.259",
                  "versionStartIncluding": "5.9",
                  "vulnerable": true
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                  "versionEndExcluding": "5.15.210",
                  "versionStartIncluding": "5.9",
                  "vulnerable": true
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                {
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                  "versionEndExcluding": "7.1",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()\n\nskb_tunnel_check_pmtu() can change skb-\u003ehead.\n\nReusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.\n\nUse instead ip_hdr(skb) as done in drivers/net/bareudp.c\nand drivers/net/geneve.c.\n\nFound by Sashiko."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is in VXLAN transmit processing reached when network-originated packets are decapsulated, bridged, and re-encapsulated; VXLAN is a UDP-based overlay protocol reachable from remote peers over the network.\nAC:L - An attacker can reliably trigger the bug by sending crafted oversized inner IPv4/IPv6 packets (e.g., with DF set or ICMP/ICMPv6 payloads) through a bridged VXLAN interface to force skb_tunnel_check_pmtu() to reallocate skb-\u003ehead yet return 0, leaving the cached ip_hdr pointer stale.\nPR:N - Exploitation requires only the ability to send VXLAN/inner IP traffic to a host with an active VXLAN bridge port; no local account, capabilities, or authentication on the victim is needed.\nUI:N - No victim user action is required beyond normal network operation; triggering the bug is entirely driven by attacker-supplied packets forwarded through the VXLAN device.\nS:U - The vulnerability corrupts kernel heap memory on the host processing the VXLAN traffic; impact remains within the kernel\u0027s security authority and does not inherently cross a VM or sandbox boundary.\nC:H - This is a use-after-free where ip_tunnel_ecn_encap() reads from a freed skb head via the stale cached ip_hdr pointer, enabling kernel memory disclosure and supporting further exploitation.\nI:H - Use-after-free on skb data provides a foundation for heap grooming and arbitrary memory write primitives that could be leveraged for kernel code execution or privilege escalation.\nA:H - The UAF can cause kernel oops/panic during transmit processing and is independently exploitable for denial of service even when full code execution is not achieved."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:57.287Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0"
        },
        {
          "url": "https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a"
        },
        {
          "url": "https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd"
        },
        {
          "url": "https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d"
        },
        {
          "url": "https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb"
        },
        {
          "url": "https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7"
        },
        {
          "url": "https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea"
        },
        {
          "url": "https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf"
        }
      ],
      "title": "vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63993",
    "datePublished": "2026-07-19T14:56:13.218Z",
    "dateReserved": "2026-07-19T07:54:57.025Z",
    "dateUpdated": "2026-08-05T12:37:57.287Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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