FKIE_CVE-2026-74727

Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-10-14 13:10
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: ovpn: skip rehash for peers already removed from by_id ovpn_nl_peer_set_doit() resolves the target peer via ovpn_peer_get_by_id() before taking ovpn->lock. In the window between the lookup (which only takes a refcount) and the subsequent spin_lock_bh(&ovpn->lock), a concurrent OVPN_CMD_PEER_DEL, keepalive expiry, or socket teardown can take ovpn->lock first, run ovpn_peer_remove() to unhash the peer from all four tables (by_id, by_vpn_addr4/6, by_transp_addr) and release the lock. set_doit then acquires ovpn->lock and calls ovpn_peer_hash_vpn_ip(), which re-inserts the now-removed peer back into the rehashing tables. The same race affects the float path: ovpn_peer_endpoints_update() holds only a refcount and acquires ovpn->lock very late (after async AEAD decrypt and a netlink notification), then rehashes the peer in the by_transp_addr table. The resurrected peer becomes reachable again from the RX lookup (ovpn_peer_get_by_transp_addr) and the TX VPN-IP lookup, even though userspace believes it is gone. Once the data-path refcount drops the peer is freed via call_rcu while the hash entries embedded in it remain linked, opening a UAF window. Bail out of the rehash when hash_entry_id is unhashed, mirroring the sentinel already used by ovpn_peer_remove() to detect the already-removed state. The check is safe under ovpn->lock, which serializes every mutation of hash_entry_id, and is a no-op for the add path because ovpn_peer_add_mp() inserts hash_entry_id before calling ovpn_peer_hash_vpn_ip().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/33ec10567fe14456063daf549fdf1a4f53448e4c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/66745480298775f188b2f5ad266643e85a90f73b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d20c181088984b6eaa8d7fe7cb5ab3510988df59
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/ovpn/peer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d20c181088984b6eaa8d7fe7cb5ab3510988df59",
              "status": "affected",
              "version": "1d36a36f6d5347360ef9681a05f6166683bafd1d",
              "versionType": "git"
            },
            {
              "lessThan": "66745480298775f188b2f5ad266643e85a90f73b",
              "status": "affected",
              "version": "1d36a36f6d5347360ef9681a05f6166683bafd1d",
              "versionType": "git"
            },
            {
              "lessThan": "33ec10567fe14456063daf549fdf1a4f53448e4c",
              "status": "affected",
              "version": "1d36a36f6d5347360ef9681a05f6166683bafd1d",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/ovpn/peer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "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\novpn: skip rehash for peers already removed from by_id\n\novpn_nl_peer_set_doit() resolves the target peer via\novpn_peer_get_by_id() before taking ovpn-\u003elock. In the window between\nthe lookup (which only takes a refcount) and the subsequent\nspin_lock_bh(\u0026ovpn-\u003elock), a concurrent OVPN_CMD_PEER_DEL, keepalive\nexpiry, or socket teardown can take ovpn-\u003elock first, run\novpn_peer_remove() to unhash the peer from all four tables (by_id,\nby_vpn_addr4/6, by_transp_addr) and release the lock. set_doit then\nacquires ovpn-\u003elock and calls ovpn_peer_hash_vpn_ip(), which\nre-inserts the now-removed peer back into the rehashing tables.\n\nThe same race affects the float path: ovpn_peer_endpoints_update()\nholds only a refcount and acquires ovpn-\u003elock very late (after async\nAEAD decrypt and a netlink notification), then rehashes the peer\nin the by_transp_addr table.\n\nThe resurrected peer becomes reachable again from the RX lookup\n(ovpn_peer_get_by_transp_addr) and the TX VPN-IP lookup, even though\nuserspace believes it is gone. Once the data-path refcount drops the\npeer is freed via call_rcu while the hash entries embedded in it\nremain linked, opening a UAF window.\n\nBail out of the rehash when hash_entry_id is unhashed, mirroring\nthe sentinel already used by ovpn_peer_remove() to detect the\nalready-removed state. The check is safe under ovpn-\u003elock, which\nserializes every mutation of hash_entry_id, and is a no-op for the\nadd path because ovpn_peer_add_mp() inserts hash_entry_id before\ncalling ovpn_peer_hash_vpn_ip()."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\novpn: omitir el rehash para pares ya eliminados de by_id\n\novpn_nl_peer_set_doit() resuelve el par objetivo a trav\u00e9s de ovpn_peer_get_by_id() antes de tomar ovpn -\u003e lock. En la ventana entre la b\u00fasqueda (que solo toma un refcount) y el subsiguiente spin_lock_bh(\u0026ovpn -\u003e lock), un OVPN_CMD_PEER_DEL concurrente, la expiraci\u00f3n de un keepalive o el cierre de un socket pueden tomar ovpn -\u003e lock primero, ejecutar ovpn_peer_remove() para deshashear el par de las cuatro tablas (by_id, by_vpn_addr4/6, by_transp_addr) y liberar el bloqueo. set_doit luego adquiere ovpn -\u003e lock y llama a ovpn_peer_hash_vpn_ip(), lo que reinserta el par ahora eliminado de nuevo en las tablas de rehashing.\n\nLa misma condici\u00f3n de carrera afecta la ruta flotante: ovpn_peer_endpoints_update() solo mantiene un refcount y adquiere ovpn -\u003e lock muy tarde (despu\u00e9s de un descifrado AEAD as\u00edncrono y una notificaci\u00f3n netlink), luego rehashea el par en la tabla by_transp_addr.\n\nEl par resucitado vuelve a ser accesible desde la b\u00fasqueda RX (ovpn_peer_get_by_transp_addr) y la b\u00fasqueda TX VPN-IP, aunque el userspace cree que ha desaparecido. Una vez que el refcount de la ruta de datos disminuye, el par es liberado a trav\u00e9s de call_rcu mientras que las entradas de hash incrustadas en \u00e9l permanecen vinculadas, abriendo una ventana UAF.\n\nSalir del rehash cuando hash_entry_id es deshasheado, reflejando el centinela ya utilizado por ovpn_peer_remove() para detectar el estado ya eliminado. La verificaci\u00f3n es segura bajo ovpn -\u003e lock, que serializa cada mutaci\u00f3n de hash_entry_id, y es una operaci\u00f3n nula para la ruta de adici\u00f3n porque ovpn_peer_add_mp() inserta hash_entry_id antes de llamar a ovpn_peer_hash_vpn_ip()."
    }
  ],
  "id": "CVE-2026-74727",
  "lastModified": "2026-10-14T13:10:00.187",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-22T16:16:47.813",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/33ec10567fe14456063daf549fdf1a4f53448e4c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/66745480298775f188b2f5ad266643e85a90f73b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d20c181088984b6eaa8d7fe7cb5ab3510988df59"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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