FKIE_CVE-2026-98122

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-09-25 15:18
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: vxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del() vxlan_mdb_is_valid_source(), which validates MDBE_ATTR_SOURCE and every MDBE_ATTR_SRC_LIST member, accepts the all-zeros address. A source list is only accepted on a (*, G) entry, whose source is the all-zeros address, and for each member of the list an (S, G) entry is derived from it by substituting the source. Entries are keyed by a plain memcmp() of struct vxlan_mdb_entry_key, so if MDBE_ATTR_SOURCE is present and holds the all-zeros address and the source list holds it as well, the derived (S, G) key is byte-identical to the (*, G) key and resolves to the same entry. Omitting MDBE_ATTR_SOURCE is not equivalent, as the key is then left with a zero address family. vxlan_mdb_remote_src_del() removes the forwarding entry of a source before freeing the source entry: vxlan_mdb_remote_src_fwd_del(vxlan, group, remote, &ent->addr); vxlan_mdb_remote_src_entry_del(ent); With the keys aliased, the first call deletes the remote of the entry that owns 'ent' instead of a separate (S, G) entry, and frees 'ent'. The second call then runs on the freed entry, and its hlist_del() reads ->pprev and ->next out of it and writes through them. Adding the (*, G) entry with NLM_F_REPLACE and no source list marks the all-zeros source for deletion and reaches this from the sweep at the end of vxlan_mdb_remote_srcs_replace(). BUG: KASAN: slab-use-after-free in __vxlan_mdb_add+0x1cd/0xd70 Read of size 8 at addr ffff888102852500 by task poc/84 __vxlan_mdb_add+0x1cd/0xd70 vxlan_mdb_add+0xc0/0x140 rtnl_mdb_add+0x157/0x2a0 rtnetlink_rcv_msg+0x207/0x5a0 Allocated by task 84: __kmalloc_cache_noprof+0x153/0x360 vxlan_mdb_remote_srcs_add+0x2eb/0x440 __vxlan_mdb_add+0x803/0xd70 Freed by task 84: kfree+0x14c/0x3b0 vxlan_mdb_remote_del+0x129/0x1a0 __vxlan_mdb_del+0x4f/0xe0 vxlan_mdb_remote_src_fwd_del.isra.0+0x162/0x1b0 __vxlan_mdb_add+0x1c5/0xd70 The MDB operations are netns-scoped, so an unprivileged user can perform them in a new user and network namespace. Reject the all-zeros address in vxlan_mdb_is_valid_source(), which covers both call sites. A (*, G) entry is expressed by omitting the source, so nothing legitimate is refused. Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4aa61c88b4e292e10abdfd791334b8272108d68a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/71203a41d6fa2fa0ea2f3a7541987958bd3694fd
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/74e2a56c82209b0335b53e25f19f9b0590e2483d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e12c903fd13c6261b98ca18d8f70ac26e739e2f8
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/vxlan/vxlan_mdb.c",
            "tools/testing/selftests/net/test_vxlan_mdb.sh"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e12c903fd13c6261b98ca18d8f70ac26e739e2f8",
              "status": "affected",
              "version": "a3a48de5eade770e911d35291217bdd69ce04ef1",
              "versionType": "git"
            },
            {
              "lessThan": "74e2a56c82209b0335b53e25f19f9b0590e2483d",
              "status": "affected",
              "version": "a3a48de5eade770e911d35291217bdd69ce04ef1",
              "versionType": "git"
            },
            {
              "lessThan": "71203a41d6fa2fa0ea2f3a7541987958bd3694fd",
              "status": "affected",
              "version": "a3a48de5eade770e911d35291217bdd69ce04ef1",
              "versionType": "git"
            },
            {
              "lessThan": "4aa61c88b4e292e10abdfd791334b8272108d68a",
              "status": "affected",
              "version": "a3a48de5eade770e911d35291217bdd69ce04ef1",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/vxlan/vxlan_mdb.c",
            "tools/testing/selftests/net/test_vxlan_mdb.sh"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "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\nvxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del()\n\nvxlan_mdb_is_valid_source(), which validates MDBE_ATTR_SOURCE and every\nMDBE_ATTR_SRC_LIST member, accepts the all-zeros address.\n\nA source list is only accepted on a (*, G) entry, whose source is the\nall-zeros address, and for each member of the list an (S, G) entry is\nderived from it by substituting the source. Entries are keyed by a plain\nmemcmp() of struct vxlan_mdb_entry_key, so if MDBE_ATTR_SOURCE is present\nand holds the all-zeros address and the source list holds it as well, the\nderived (S, G) key is byte-identical to the (*, G) key and resolves to the\nsame entry. Omitting MDBE_ATTR_SOURCE is not equivalent, as the key is\nthen left with a zero address family.\n\nvxlan_mdb_remote_src_del() removes the forwarding entry of a source before\nfreeing the source entry:\n\n\tvxlan_mdb_remote_src_fwd_del(vxlan, group, remote, \u0026ent-\u003eaddr);\n\tvxlan_mdb_remote_src_entry_del(ent);\n\nWith the keys aliased, the first call deletes the remote of the entry that\nowns \u0027ent\u0027 instead of a separate (S, G) entry, and frees \u0027ent\u0027. The second\ncall then runs on the freed entry, and its hlist_del() reads -\u003epprev and\n-\u003enext out of it and writes through them.\n\nAdding the (*, G) entry with NLM_F_REPLACE and no source list marks the\nall-zeros source for deletion and reaches this from the sweep at the end\nof vxlan_mdb_remote_srcs_replace().\n\n  BUG: KASAN: slab-use-after-free in __vxlan_mdb_add+0x1cd/0xd70\n  Read of size 8 at addr ffff888102852500 by task poc/84\n   __vxlan_mdb_add+0x1cd/0xd70\n   vxlan_mdb_add+0xc0/0x140\n   rtnl_mdb_add+0x157/0x2a0\n   rtnetlink_rcv_msg+0x207/0x5a0\n  Allocated by task 84:\n   __kmalloc_cache_noprof+0x153/0x360\n   vxlan_mdb_remote_srcs_add+0x2eb/0x440\n   __vxlan_mdb_add+0x803/0xd70\n  Freed by task 84:\n   kfree+0x14c/0x3b0\n   vxlan_mdb_remote_del+0x129/0x1a0\n   __vxlan_mdb_del+0x4f/0xe0\n   vxlan_mdb_remote_src_fwd_del.isra.0+0x162/0x1b0\n   __vxlan_mdb_add+0x1c5/0xd70\n\nThe MDB operations are netns-scoped, so an unprivileged user can perform\nthem in a new user and network namespace.\n\nReject the all-zeros address in vxlan_mdb_is_valid_source(), which covers\nboth call sites. A (*, G) entry is expressed by omitting the source, so\nnothing legitimate is refused.\n\nDiscovered by XBOW, triaged by Baul Lee \u003cbaul.lee@xbow.com\u003e"
    }
  ],
  "id": "CVE-2026-98122",
  "lastModified": "2026-09-25T15:18:06.580",
  "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"
      }
    ]
  },
  "published": "2026-09-25T11:17:43.470",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4aa61c88b4e292e10abdfd791334b8272108d68a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/71203a41d6fa2fa0ea2f3a7541987958bd3694fd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/74e2a56c82209b0335b53e25f19f9b0590e2483d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e12c903fd13c6261b98ca18d8f70ac26e739e2f8"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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