CVE-2026-64450 (GCVE-0-2026-64450)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:51 – Updated: 2026-08-17 04:55
VLAI
Title
tipc: fix out-of-bounds read in broadcast Gap ACK blocks
Summary
In the Linux kernel, the following vulnerability has been resolved: tipc: fix out-of-bounds read in broadcast Gap ACK blocks A broadcast PROTOCOL/STATE_MSG can carry a Gap ACK blocks record in its data area. tipc_get_gap_ack_blks() only verifies that the record's len field is self-consistent with its ugack_cnt/bgack_cnt counts (sz == struct_size(p, gacks, ugack_cnt + bgack_cnt)); it does not check that the record actually fits in the message data area, msg_data_sz(). The unicast caller tipc_link_proto_rcv() bounds it ("if (glen > dlen) break;"), but the broadcast caller tipc_bcast_sync_rcv() discards the returned size, so tipc_link_advance_transmq() copies the record off the receive skb with an attacker-controlled count: this_ga = kmemdup(ga, struct_size(ga, gacks, ga->bgack_cnt), GFP_ATOMIC); A TIPC neighbour that negotiated TIPC_GAP_ACK_BLOCK triggers it with one ordinary broadcast STATE_MSG (msg_bc_ack_invalid() clear), sized so its data area is short, carrying a Gap ACK record with len = 0x400, bgack_cnt = 0xff and ugack_cnt = 0. len then equals struct_size(p, gacks, 255), so the consistency check passes and ga is non-NULL; kmemdup() reads struct_size(ga, gacks, 255) = 1024 bytes out of the much smaller skb: BUG: KASAN: slab-out-of-bounds in kmemdup_noprof+0x48/0x60 Read of size 1024 at addr ffff0000c7030d38 by task poc864/69 Call trace: kmemdup_noprof+0x48/0x60 tipc_link_advance_transmq+0x86c/0xb80 tipc_link_bc_ack_rcv+0x19c/0x1e0 tipc_bcast_sync_rcv+0x1c4/0x2c4 tipc_rcv+0x85c/0x1340 tipc_l2_rcv_msg+0xac/0x104 The buggy address belongs to the object at ffff0000c7030d00 which belongs to the cache skbuff_small_head of size 704 The buggy address is located 56 bytes inside of allocated 704-byte region [ffff0000c7030d00, ffff0000c7030fc0) The copied-out bytes are subsequently consumed as gap/ack values, but the read is already out of bounds at the kmemdup() regardless of how they are used. The unicast STATE path drops such a message: "if (glen > dlen) break;" skips the rest of STATE_MSG handling and the skb is freed. Make the broadcast path drop it too. tipc_bcast_sync_rcv() now bounds the record against msg_data_sz() and, when it does not fit, reports it back through tipc_node_bc_sync_rcv() to tipc_rcv() so the skb is discarded rather than processed. ga is not cleared on this path: ga == NULL already means "legacy peer without Selective ACK", a distinct legitimate state.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < 055663d21dc4336f67933ab26bef3c5934be6324 (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < 016f5995c37a5a2c45198308f830f244517d70b7 (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < 74b45af86a767594ba52330cd440ea84e24d700d (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < 9a51115fcdc78687c8852bf93a1db3951dbb223b (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < a21ed5064217cc33726da6c7ef1a520eba43aea1 (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < 2de42e268174766cb2e2b90721afdfdff70e0d8d (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < f333b6851bdf326fd2134133272dbbed0c94d921 (git)
Affected: d7626b5acff9227e2a65da636a53e09bdafdc0aa , < 2b66974a1b6134a4bbc3bfed181f7418f688eb54 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.8
Unaffected: 0 , < 5.8 (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: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix out-of-bounds read in broadcast Gap ACK blocks\n\nA broadcast PROTOCOL/STATE_MSG can carry a Gap ACK blocks record in its\ndata area. tipc_get_gap_ack_blks() only verifies that the record\u0027s len\nfield is self-consistent with its ugack_cnt/bgack_cnt counts\n(sz == struct_size(p, gacks, ugack_cnt + bgack_cnt)); it does not check\nthat the record actually fits in the message data area, msg_data_sz().\n\nThe unicast caller tipc_link_proto_rcv() bounds it (\"if (glen \u003e dlen)\nbreak;\"), but the broadcast caller tipc_bcast_sync_rcv() discards the\nreturned size, so tipc_link_advance_transmq() copies the record off the\nreceive skb with an attacker-controlled count:\n\n\tthis_ga = kmemdup(ga, struct_size(ga, gacks, ga-\u003ebgack_cnt),\n\t\t\t  GFP_ATOMIC);\n\nA TIPC neighbour that negotiated TIPC_GAP_ACK_BLOCK triggers it with one\nordinary broadcast STATE_MSG (msg_bc_ack_invalid() clear), sized so its\ndata area is short, carrying a Gap ACK record with len = 0x400,\nbgack_cnt = 0xff and ugack_cnt = 0. len then equals\nstruct_size(p, gacks, 255), so the consistency check passes and ga is\nnon-NULL; kmemdup() reads struct_size(ga, gacks, 255) = 1024 bytes out\nof the much smaller skb:\n\n  BUG: KASAN: slab-out-of-bounds in kmemdup_noprof+0x48/0x60\n  Read of size 1024 at addr ffff0000c7030d38 by task poc864/69\n  Call trace:\n   kmemdup_noprof+0x48/0x60\n   tipc_link_advance_transmq+0x86c/0xb80\n   tipc_link_bc_ack_rcv+0x19c/0x1e0\n   tipc_bcast_sync_rcv+0x1c4/0x2c4\n   tipc_rcv+0x85c/0x1340\n   tipc_l2_rcv_msg+0xac/0x104\n  The buggy address belongs to the object at ffff0000c7030d00\n   which belongs to the cache skbuff_small_head of size 704\n  The buggy address is located 56 bytes inside of\n   allocated 704-byte region [ffff0000c7030d00, ffff0000c7030fc0)\n\nThe copied-out bytes are subsequently consumed as gap/ack values, but\nthe read is already out of bounds at the kmemdup() regardless of how\nthey are used.\n\nThe unicast STATE path drops such a message: \"if (glen \u003e dlen) break;\"\nskips the rest of STATE_MSG handling and the skb is freed. Make the\nbroadcast path drop it too. tipc_bcast_sync_rcv() now bounds the record\nagainst msg_data_sz() and, when it does not fit, reports it back through\ntipc_node_bc_sync_rcv() to tipc_rcv() so the skb is discarded rather than\nprocessed. ga is not cleared on this path: ga == NULL already means\n\"legacy peer without Selective ACK\", a distinct legitimate state."
        }
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
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              "value": "AV:N - TIPC packets can arrive through an IP/UDP bearer from a routable remote source, and the receive callback does not restrict packets to configured remote addresses. An attacker can also establish or spoof the required TIPC neighbour state without credentials.\nAC:L - The attacker controls capability advertisement, link establishment, broadcast synchronization, and the malformed STATE message; one packet then reliably performs the out-of-bounds copy without a race or uncontrollable condition.\nPR:N - The packet-receive path performs no capability or user-credential check, and TIPC discovery and link negotiation are unauthenticated when optional cryptographic keys are not configured. The vulnerable broadcast processing also precedes normal STATE-session validation.\nUI:N - No victim action is required after the TIPC bearer is active; receipt of the crafted STATE message directly invokes the vulnerable code.\nS:U - The vulnerability compromises availability and potentially confidentiality within the receiving kernel\u0027s existing security authority, without crossing a VM, IOMMU, or comparable scope boundary.\nC:H - The attacker-controlled count makes the kernel copy up to 1,024 bytes from a much smaller skb, incorporating substantial adjacent slab contents rather than a strictly bounded few-byte read.\nI:N - The defect performs an out-of-bounds read into a correctly sized new allocation; investigation found no out-of-bounds write, arbitrary-write primitive, or control-flow corruption.\nA:H - The demonstrated 1,024-byte slab-out-of-bounds access produces a KASAN BUG and can panic or fault hardened kernels, and an unauthenticated attacker can trigger it repeatedly."
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        {
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        {
          "url": "https://git.kernel.org/stable/c/2b66974a1b6134a4bbc3bfed181f7418f688eb54"
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      "title": "tipc: fix out-of-bounds read in broadcast Gap ACK blocks",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64450",
    "datePublished": "2026-07-25T08:51:20.319Z",
    "dateReserved": "2026-07-19T15:36:31.788Z",
    "dateUpdated": "2026-08-17T04:55:54.043Z",
    "state": "PUBLISHED"
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      "date": "2026-09-21",
      "epss": "0.00537",
      "percentile": "0.43985"
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    "microsoft_vex": {
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      "cve": "CVE-2026-64450",
      "id": "msrc_CVE-2026-64450",
      "initial_release_date": "2026-07-26T01:06:52.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "tipc: fix out-of-bounds read in broadcast Gap ACK blocks",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64450.json",
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                "negate": false,
                "operator": "OR"
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            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix out-of-bounds read in broadcast Gap ACK blocks\n\nA broadcast PROTOCOL/STATE_MSG can carry a Gap ACK blocks record in its\ndata area. tipc_get_gap_ack_blks() only verifies that the record\u0027s len\nfield is self-consistent with its ugack_cnt/bgack_cnt counts\n(sz == struct_size(p, gacks, ugack_cnt + bgack_cnt)); it does not check\nthat the record actually fits in the message data area, msg_data_sz().\n\nThe unicast caller tipc_link_proto_rcv() bounds it (\"if (glen \u003e dlen)\nbreak;\"), but the broadcast caller tipc_bcast_sync_rcv() discards the\nreturned size, so tipc_link_advance_transmq() copies the record off the\nreceive skb with an attacker-controlled count:\n\n\tthis_ga = kmemdup(ga, struct_size(ga, gacks, ga-\u003ebgack_cnt),\n\t\t\t  GFP_ATOMIC);\n\nA TIPC neighbour that negotiated TIPC_GAP_ACK_BLOCK triggers it with one\nordinary broadcast STATE_MSG (msg_bc_ack_invalid() clear), sized so its\ndata area is short, carrying a Gap ACK record with len = 0x400,\nbgack_cnt = 0xff and ugack_cnt = 0. len then equals\nstruct_size(p, gacks, 255), so the consistency check passes and ga is\nnon-NULL; kmemdup() reads struct_size(ga, gacks, 255) = 1024 bytes out\nof the much smaller skb:\n\n  BUG: KASAN: slab-out-of-bounds in kmemdup_noprof+0x48/0x60\n  Read of size 1024 at addr ffff0000c7030d38 by task poc864/69\n  Call trace:\n   kmemdup_noprof+0x48/0x60\n   tipc_link_advance_transmq+0x86c/0xb80\n   tipc_link_bc_ack_rcv+0x19c/0x1e0\n   tipc_bcast_sync_rcv+0x1c4/0x2c4\n   tipc_rcv+0x85c/0x1340\n   tipc_l2_rcv_msg+0xac/0x104\n  The buggy address belongs to the object at ffff0000c7030d00\n   which belongs to the cache skbuff_small_head of size 704\n  The buggy address is located 56 bytes inside of\n   allocated 704-byte region [ffff0000c7030d00, ffff0000c7030fc0)\n\nThe copied-out bytes are subsequently consumed as gap/ack values, but\nthe read is already out of bounds at the kmemdup() regardless of how\nthey are used.\n\nThe unicast STATE path drops such a message: \"if (glen \u003e dlen) break;\"\nskips the rest of STATE_MSG handling and the skb is freed. Make the\nbroadcast path drop it too. tipc_bcast_sync_rcv() now bounds the record\nagainst msg_data_sz() and, when it does not fit, reports it back through\ntipc_node_bc_sync_rcv() to tipc_rcv() so the skb is discarded rather than\nprocessed. ga is not cleared on this path: ga == NULL already means\n\"legacy peer without Selective ACK\", a distinct legitimate state."
          }
        ],
        "id": "CVE-2026-64450",
        "lastModified": "2026-09-03T15:31:34.900",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.1,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 5.2,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-25T10:17:29.850",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/016f5995c37a5a2c45198308f830f244517d70b7"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/055663d21dc4336f67933ab26bef3c5934be6324"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/2b66974a1b6134a4bbc3bfed181f7418f688eb54"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/2de42e268174766cb2e2b90721afdfdff70e0d8d"
          },
          {
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            "tags": [
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/9a51115fcdc78687c8852bf93a1db3951dbb223b"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/a21ed5064217cc33726da6c7ef1a520eba43aea1"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/f333b6851bdf326fd2134133272dbbed0c94d921"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-125"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-02T21:53:49+00:00",
      "cve": "CVE-2026-64450",
      "id": "CVE-2026-64450",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "43",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tipc: fix out-of-bounds read in broadcast Gap ACK blocks",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64450.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-18T00:40:00Z",
      "cve": "CVE-2026-64450",
      "id": "CVE-2026-64450",
      "initial_release_date": "2026-07-25T15:59:07Z",
      "product_status:first_fixed": "104",
      "product_status:known_affected": "727",
      "product_status:known_not_affected": "6",
      "product_status:recommended": "111",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64450",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64450.json",
      "version": "12"
    }
  }
}



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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

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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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.