CVE-2023-53559 (GCVE-0-2023-53559)
Vulnerability from cvelistv5
Published
2025-10-04 15:17
Modified
2026-08-05 09:14
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: ip_vti: fix potential slab-use-after-free in decode_session6 When ip_vti device is set to the qdisc of the sfb type, the cb field of the sent skb may be modified during enqueuing. Then, slab-use-after-free may occur when ip_vti device sends IPv6 packets. As commit f855691975bb ("xfrm6: Fix the nexthdr offset in _decode_session6.") showed, xfrm_decode_session was originally intended only for the receive path. IP6CB(skb)->nhoff is not set during transmission. Therefore, set the cb field in the skb to 0 before sending packets.
References
Impacted products
Vendor Product Version
Linux Linux Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
Version: f855691975bb06373a98711e4cfe2c224244b536
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/ip_vti.c"
          ],
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          "vendor": "Linux",
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          "vendor": "Linux",
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              "version": "3.19"
            },
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              "version": "0",
              "versionType": "semver"
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              "version": "4.14.324",
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            },
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              "version": "4.19.293",
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            },
            {
              "lessThanOrEqual": "5.4.*",
              "status": "unaffected",
              "version": "5.4.255",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.192",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.128",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.1.47",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "6.4.12",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "vulnerable": true
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                  "versionEndExcluding": "6.5",
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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\nip_vti: fix potential slab-use-after-free in decode_session6\n\nWhen ip_vti device is set to the qdisc of the sfb type, the cb field\nof the sent skb may be modified during enqueuing. Then,\nslab-use-after-free may occur when ip_vti device sends IPv6 packets.\nAs commit f855691975bb (\"xfrm6: Fix the nexthdr offset in\n_decode_session6.\") showed, xfrm_decode_session was originally intended\nonly for the receive path. IP6CB(skb)-\u003enhoff is not set during\ntransmission. Therefore, set the cb field in the skb to 0 before\nsending packets."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Triggering requires a locally configured ip_vti device with an sfb qdisc attached and packets routed out of it, all of which is set up and driven through local netlink/rtnetlink and a local socket. Although forwarded traffic from a remote peer would also hit vti_tunnel_xmit on a router so configured, the vulnerable state depends entirely on local device/qdisc configuration, so Local is the defensible vector.\nAC:L - The attacker creates every precondition: the vti device, the sfb qdisc, and its rehash_interval/warmup_time tunables that control when q-\u003eslot flips and hashes[1] is populated with a siphash value overlapping IP6CB-\u003enhoff. Once slot==1 every transmitted IPv6 packet performs the wild nh[nhoff] read, making the trigger deterministic and repeatable.\nPR:L - Creating the vti tunnel and attaching the sfb qdisc requires CAP_NET_ADMIN, but ip_vti is fully network-namespace aware (register_pernet_device with a per-netns ip_vti0 fallback), so an unprivileged user obtains the needed capability with unshare -Urn. Per kernel scoring guidance, CAP_NET_ADMIN reachable through user namespaces is Low, not High.\nUI:N - The attacker performs the entire sequence \u2014 configure the device and qdisc, add a route, send an IPv6 packet \u2014 with no action by any other user or administrator.\nS:U - The out-of-bounds access occurs in kernel heap memory and its consequences remain within the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - decode_session6() reads a byte from freed or adjacent slab memory at an offset up to 64KB beyond the network header \u2014 an unbounded use-after-free read rather than a small bounded one \u2014 and that value steers the protocol state machine and xfrm flow key, providing an oracle on kernel heap contents.\nI:H - The kernel\u0027s IPsec flow decode (flowi6_proto, ports, and the ensuing ip6_route_output/xfrm_lookup_route policy selection) is driven by data read out of freed heap memory, so a security-relevant kernel decision is made on corrupted state; consistent with treating slab-use-after-free as a high integrity impact.\nA:H - The wild read dereferences an address up to 65535 bytes past the skb data allocation, which faults on unmapped memory or memory holes and reliably produces a KASAN slab-use-after-free splat and kernel oops. The attacker can repeat it on every transmitted packet, so it is a sustained crash/DoS."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:14:50.051Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/82fb41c5de243e7dfa90f32ca58e35adaff56c1d"
        },
        {
          "url": "https://git.kernel.org/stable/c/7dfe23659f3677c08a60a0056cda2d91a79c15ca"
        },
        {
          "url": "https://git.kernel.org/stable/c/d34c30442d5e53a33cde79ca163320dbe2432cbd"
        },
        {
          "url": "https://git.kernel.org/stable/c/0b4d69539fdea138af2befe08893850c89248068"
        },
        {
          "url": "https://git.kernel.org/stable/c/e1e04cc2ef2c0c0866c19f5627149a76c2baae32"
        },
        {
          "url": "https://git.kernel.org/stable/c/2b05bf5dc437f7891dd409a3eaf5058459391c7a"
        },
        {
          "url": "https://git.kernel.org/stable/c/78e397a43e1c47321a4679cc49a6c4530bf820b9"
        },
        {
          "url": "https://git.kernel.org/stable/c/6018a266279b1a75143c7c0804dd08a5fc4c3e0b"
        }
      ],
      "title": "ip_vti: fix potential slab-use-after-free in decode_session6",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53559",
    "datePublished": "2025-10-04T15:17:03.497Z",
    "dateReserved": "2025-10-04T15:14:15.923Z",
    "dateUpdated": "2026-08-05T09:14:50.051Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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