CVE-2026-74475 (GCVE-0-2026-74475)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:27 – Updated: 2026-08-17 05:47
VLAI
Title
vxlan: use neigh_ha_snapshot() in route_shortcircuit()
Summary
In the Linux kernel, the following vulnerability has been resolved: vxlan: use neigh_ha_snapshot() in route_shortcircuit() The neighbour hardware address n->ha can be updated asynchronously by the neighbour subsystem, protected by n->ha_lock seqlock. Reading n->ha without holding the seqlock loop can lead to torn reads or reading a partially updated MAC address. Use neigh_ha_snapshot() in route_shortcircuit() to safely copy n->ha under read_seqbegin()/read_seqretry() lock protection before using it. Note that arp_reduce() and neigh_reduce() seem to have the same issue left for future patches.
Severity
10 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e4f67addf158f98f8197e08974966b18480dc751 , < d08e8ac13f2e228cc7fc3c70b5ebe71557b624a0 (git)
Affected: e4f67addf158f98f8197e08974966b18480dc751 , < ec341bb76d77b4c2948764375ee6bfeef4bb41c3 (git)
Affected: e4f67addf158f98f8197e08974966b18480dc751 , < ff89415d34c3ab9f5312316423122e664ed3524f (git)
Affected: e4f67addf158f98f8197e08974966b18480dc751 , < 05f2987f73daa05333fd713d05546142f9f7c5f0 (git)
Affected: e4f67addf158f98f8197e08974966b18480dc751 , < 8eca411347e1d38964f9ed2c8d3b6ab0e7e4473d (git)
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Linux Linux Affected: 3.8
Unaffected: 0 , < 3.8 (semver)
Unaffected: 6.6.151 , ≤ 6.6.* (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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        {
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          "product": "Linux",
          "programFiles": [
            "drivers/net/vxlan/vxlan_core.c"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: use neigh_ha_snapshot() in route_shortcircuit()\n\nThe neighbour hardware address n-\u003eha can be updated asynchronously by the\nneighbour subsystem, protected by n-\u003eha_lock seqlock. Reading n-\u003eha without\nholding the seqlock loop can lead to torn reads or reading a partially updated\nMAC address.\n\nUse neigh_ha_snapshot() in route_shortcircuit() to safely copy n-\u003eha under\nread_seqbegin()/read_seqretry() lock protection before using it.\n\nNote that arp_reduce() and neigh_reduce() seem to have the same issue\nleft for future patches."
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            "baseSeverity": "CRITICAL",
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            "version": "3.1"
          },
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              "lang": "en",
              "value": "AV:N - route_shortcircuit() runs on the vxlan_xmit() transmit path when overlay IP/IPv6 traffic is encapsulated; in cloud/SDN VTEP deployments a remote tenant can drive dev_queue_xmit() through bridge/IP forwarding without any local syscall or netlink access.\nAC:L - The attacker controls both sides of the race by concurrently sending overlay traffic that hits route_shortcircuit() and generating neighbour ha updates (ARP/NDP churn); repeated attempts do not depend on victim state or uncontrollable memory layout.\nPR:N - Exploitation requires only the ability to send overlay/underlay packets to a VTEP that already has VXLAN_F_RSC and router FDB entries configured by infrastructure; no CAP_NET_ADMIN, root, or host credentials are needed on the victim.\nUI:N - Triggering is automatic during kernel packet forwarding and VXLAN encapsulation once matching traffic flows; no mount, file open, or other victim action is required beyond normal overlay operation.\nS:C - A torn n-\u003eha read can rewrite the skb Ethernet destination and reselect a different FDB remote, mis-encapsulating traffic to an unintended VXLAN peer and crossing intended multi-tenant overlay segmentation boundaries beyond the local VTEP authority.\nC:H - Unsynchronized reads of neighbour ha during concurrent updates yield torn MAC values that drive post-rewrite FDB lookup and encapsulation, potentially delivering other tenants\u0027 overlay frames to an attacker-controlled remote endpoint or leaking mixed neighbour state.\nI:H - The corrupted hardware address is copied into the skb Ethernet header and steers subsequent vxlan_find_mac_tx()/vxlan_xmit_one() encapsulation, enabling deterministic overlay traffic redirection or injection toward an attacker-chosen VTEP rather than the intended router destination.\nA:L - While the host kernel does not panic, torn MAC rewriting can cause mis-encapsulation, FDB misses, and dropped or misdelivered overlay packets, producing intermittent connectivity loss and performance degradation on affected VTEP nodes under sustained attack."
            }
          ]
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      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:47:36.362Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/8eca411347e1d38964f9ed2c8d3b6ab0e7e4473d"
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    "cveId": "CVE-2026-74475",
    "datePublished": "2026-08-15T12:27:10.685Z",
    "dateReserved": "2026-08-15T05:44:03.903Z",
    "dateUpdated": "2026-08-17T05:47:36.362Z",
    "state": "PUBLISHED"
  },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T14:55:40+00:00",
      "cve": "CVE-2026-74475",
      "id": "CVE-2026-74475",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: vxlan: use neigh_ha_snapshot() in route_shortcircuit()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74475.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "critical",
      "current_release_date": "2026-08-17T16:26:42Z",
      "cve": "CVE-2026-74475",
      "id": "CVE-2026-74475",
      "initial_release_date": "2026-08-15T23:52:12Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74475",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74475.json",
      "version": "3"
    }
  }
}



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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.


Detection rules are retrieved from Rulezet.