CVE-2026-74556 (GCVE-0-2026-74556)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:28 – Updated: 2026-08-17 05:48
VLAI
Title
scsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer
Summary
In the Linux kernel, the following vulnerability has been resolved: scsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer iscsi_tcp_hdr_dissect() receives the data segment of several PDU types into the fixed-size conn->data buffer, which is allocated for ISCSI_DEF_MAX_RECV_SEG_LEN (8192) bytes. For the LOGIN_RSP, TEXT_RSP, REJECT and ASYNC_EVENT opcodes the dissect path already rejects a PDU whose DataSegmentLength exceeds that buffer. The SCSI Command Response (ISCSI_OP_SCSI_CMD_RSP) path also copies its data segment (sense/response data) into conn->data via iscsi_tcp_data_recv_prep(), but it does so without the same check. The only upstream bound on in.datalen is conn->max_recv_dlength, the initiator's advertised MaxRecvDataSegmentLength, which is commonly negotiated well above 8192 (open-iscsi defaults to 262144). A target that returns a SCSI Response with a DataSegmentLength between 8193 and max_recv_dlength therefore overflows the 8192-byte conn->data buffer. Once the same bound applies, ISCSI_OP_SCSI_CMD_RSP is handled exactly like those responses: bound the data segment, receive it into conn->data when present, and otherwise complete the PDU with no data. Fold the opcode into that case group rather than duplicating the check.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a081c13e39b5c17052a7b46fafa61019c4c110ff , < c97b5265cc47775f77fd2a23d6bde0426997b233 (git)
Affected: a081c13e39b5c17052a7b46fafa61019c4c110ff , < 084af0253673425ce2ae62e3c7f74f0dd023711b (git)
Affected: a081c13e39b5c17052a7b46fafa61019c4c110ff , < 72815741715bd41556dac5eeb068bf0f8af06ee7 (git)
Affected: a081c13e39b5c17052a7b46fafa61019c4c110ff , < b0aa3e8e2ab4ca92adb28a3ef41873b3363b8676 (git)
Affected: a081c13e39b5c17052a7b46fafa61019c4c110ff , < c1dea15f819cded9b3faf58f8bec72323568b6e6 (git)
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Linux Linux Affected: 2.6.29
Unaffected: 0 , < 2.6.29 (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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    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/scsi/libiscsi_tcp.c"
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "6.18.44",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.1.8",
              "versionType": "semver"
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer\n\niscsi_tcp_hdr_dissect() receives the data segment of several PDU types\ninto the fixed-size conn-\u003edata buffer, which is allocated for\nISCSI_DEF_MAX_RECV_SEG_LEN (8192) bytes.  For the LOGIN_RSP, TEXT_RSP,\nREJECT and ASYNC_EVENT opcodes the dissect path already rejects a PDU\nwhose DataSegmentLength exceeds that buffer.\n\nThe SCSI Command Response (ISCSI_OP_SCSI_CMD_RSP) path also copies its\ndata segment (sense/response data) into conn-\u003edata via\niscsi_tcp_data_recv_prep(), but it does so without the same check.  The\nonly upstream bound on in.datalen is conn-\u003emax_recv_dlength, the\ninitiator\u0027s advertised MaxRecvDataSegmentLength, which is commonly\nnegotiated well above 8192 (open-iscsi defaults to 262144).  A target\nthat returns a SCSI Response with a DataSegmentLength between 8193 and\nmax_recv_dlength therefore overflows the 8192-byte conn-\u003edata buffer.\n\nOnce the same bound applies, ISCSI_OP_SCSI_CMD_RSP is handled exactly\nlike those responses: bound the data segment, receive it into conn-\u003edata\nwhen present, and otherwise complete the PDU with no data.  Fold the\nopcode into that case group rather than duplicating the check."
        }
      ],
      "metrics": [
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
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              "lang": "en",
              "value": "AV:N - A malicious or compromised iSCSI target delivers crafted SCSI Command Response PDUs over the established TCP iSCSI session; reception flows through iscsi_sw_tcp_recv/iscsi_tcp_recv_skb into iscsi_tcp_hdr_dissect without local access.\nAC:L - The attacker controls the target and can set DataSegmentLength between 8193 and negotiated max_recv_dlength (open-iscsi commonly 262144) on SCSI_CMD_RSP for any outstanding command ITT; no races or victim-specific heap layout are required.\nPR:N - No privileges on the victim host are needed; a remote attacker acting as or MITMing the iSCSI target sends malicious responses after session login, independent of victim user accounts or capabilities.\nUI:N - On systems with persistent iSCSI sessions (cloud VMs, SAN-boot hosts, Kubernetes iSCSI volumes), exploitation triggers automatically during normal SCSI I/O when command responses are received; no victim action is needed at attack time.\nS:U - Heap corruption is confined to the kernel iSCSI initiator on the affected host; successful exploitation yields kernel compromise or DoS within the same security authority, not a VM escape or cross-boundary scope change.\nC:H - iscsi_tcp_segment_recv memcpy writes up to max_recv_dlength bytes into an 8192-byte conn-\u003edata buffer, causing a large heap overflow whose controlled corruption can be leveraged for arbitrary kernel memory disclosure.\nI:H - Attacker-controlled response data is copied past the fixed conn-\u003edata allocation via iscsi_tcp_data_recv_prep/iscsi_segment_init_linear, enabling heap metadata/object corruption exploitable for arbitrary kernel write and privilege escalation.\nA:H - Overflowing the conn-\u003edata heap buffer can immediately corrupt adjacent kernel allocations and cause oops/panic; a malicious target can repeatedly trigger this on active sessions to deny storage availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:48:38.659Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/c97b5265cc47775f77fd2a23d6bde0426997b233"
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          "url": "https://git.kernel.org/stable/c/c1dea15f819cded9b3faf58f8bec72323568b6e6"
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      ],
      "title": "scsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74556",
    "datePublished": "2026-08-15T12:28:01.359Z",
    "dateReserved": "2026-08-15T05:44:03.916Z",
    "dateUpdated": "2026-08-17T05:48:38.659Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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    "epss": {
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      "date": "2026-08-18",
      "epss": "0.00359",
      "percentile": "0.28981"
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    "suse_vex": {
      "aggregate_severity": "critical",
      "current_release_date": "2026-08-17T16:25:12Z",
      "cve": "CVE-2026-74556",
      "id": "CVE-2026-74556",
      "initial_release_date": "2026-08-15T23:50:20Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74556",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74556.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

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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.


Detection rules are retrieved from Rulezet.