CVE-2026-72021 (GCVE-0-2026-72021)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:51 – Updated: 2026-08-17 05:39
VLAI
Title
ipvs: use parsed transport offset in SCTP state lookup
Summary
In the Linux kernel, the following vulnerability has been resolved: ipvs: use parsed transport offset in SCTP state lookup set_sctp_state() reads the SCTP chunk header again in order to drive the IPVS SCTP state table. For IPv6 it computes the offset with sizeof(struct ipv6hdr), while the surrounding IPVS code uses iph.len from ip_vs_fill_iph_skb(), where ipv6_find_hdr() has already skipped extension headers and found the real transport header. This makes the state machine read from the wrong offset for IPv6 SCTP packets that carry extension headers. For example, an INIT packet with an 8-byte destination options header can be scheduled correctly by sctp_conn_schedule(), but set_sctp_state() reads the first byte of the SCTP verification tag as a DATA chunk type. The connection then moves from NONE to ESTABLISHED instead of INIT1, gets the longer established timeout, and updates the active/inactive destination counters incorrectly. This happens even though the SCTP handshake has not completed. Use the parsed transport offset passed down from ip_vs_set_state() for the SCTP chunk-header lookup. For IPv4 and IPv6 packets without extension headers this preserves the existing offset.
Severity
8.2 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < d2b8b1557ec07ea1bb5dddbceaf4dfe63d388e27 (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < 9f94573ab962a9e81954b755da016fa3cd2f5039 (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < 290e9e8389b556efc603522e28bd1543846aa336 (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < 9cb5ac594ca76d3a71803b23b74c835b0721e628 (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < a4a2d2e483d79cc2ad3a170674cf159644acf22b (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < 247d055504dcc852e539b9f7f30d19f9741474bf (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < e5d0bb8871668f20de8f3c94b5ae3f372346bc6e (git)
Affected: 2906f66a5682e5670a5eefe991843689b8d8563f , < 2f75c0faa3361b28e36cc0512b3299e163e25789 (git)
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Linux Linux Affected: 2.6.34
Unaffected: 0 , < 2.6.34 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipvs: use parsed transport offset in SCTP state lookup\n\nset_sctp_state() reads the SCTP chunk header again in order to drive the\nIPVS SCTP state table. For IPv6 it computes the offset with\nsizeof(struct ipv6hdr), while the surrounding IPVS code uses iph.len from\nip_vs_fill_iph_skb(), where ipv6_find_hdr() has already skipped\nextension headers and found the real transport header.\n\nThis makes the state machine read from the wrong offset for IPv6 SCTP\npackets that carry extension headers. For example, an INIT packet with an\n8-byte destination options header can be scheduled correctly by\nsctp_conn_schedule(), but set_sctp_state() reads the first byte of the\nSCTP verification tag as a DATA chunk type. The connection then moves\nfrom NONE to ESTABLISHED instead of INIT1, gets the longer established\ntimeout, and updates the active/inactive destination counters\nincorrectly. This happens even though the SCTP handshake has not\ncompleted.\n\nUse the parsed transport offset passed down from ip_vs_set_state() for\nthe SCTP chunk-header lookup. For IPv4 and IPv6 packets without\nextension headers this preserves the existing offset."
        }
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
            "version": "3.1"
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              "value": "AV:N - The bug is hit in IPVS netfilter hooks (NF_INET_LOCAL_IN/FORWARD) when remote IPv6 SCTP packets reach a configured virtual-server VIP; no local syscall or ioctl is required.\nAC:L - An attacker can reliably send SCTP INIT packets with an IPv6 Destination Options extension header so set_sctp_state() reads the wrong byte while sctp_conn_schedule() still accepts the flow, reproducing the NONE-to-ESTABLISHED misclassification every time.\nPR:N - Exploitation needs only the ability to send IPv6 SCTP traffic to the load balancer VIP; configuring IPVS requires CAP_NET_ADMIN on the target but that is an operator prerequisite, not an attacker privilege.\nUI:N - No victim interaction is required; the state machine corruption is triggered solely by attacker-crafted network packets processed automatically by the IPVS receive path.\nS:U - Impact is confined to incorrect IPVS SCTP connection state, timeouts, and backend active/inactive counters on the load balancer; it does not cross a VM, container, or IOMMU security boundary.\nC:N - The flaw misinterprets bytes inside the attacker-supplied packet (e.g., SCTP verification tag) via skb_header_pointer(); there is no out-of-bounds kernel memory read or information disclosure primitive.\nI:L - Wrong chunk-type parsing corrupts IPVS SCTP state tracking, prematurely marks associations ESTABLISHED, skews active/inactive destination counters, and can alter backend selection for load-aware schedulers without giving arbitrary kernel write.\nA:H - False ESTABLISHED transitions apply a 15-minute timeout instead of the 4-second INIT1 timeout, letting an unauthenticated remote attacker pin large numbers of bogus entries in the connection table and deny service on the affected VIP."
            }
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        "dateUpdated": "2026-08-17T05:39:31.586Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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    "datePublished": "2026-08-15T05:51:47.324Z",
    "dateReserved": "2026-08-09T03:40:39.900Z",
    "dateUpdated": "2026-08-17T05:39:31.586Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T16:59:39+00:00",
      "cve": "CVE-2026-72021",
      "id": "CVE-2026-72021",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ipvs: use parsed transport offset in SCTP state lookup",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72021.json",
      "version": "3"
    }
  }
}



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