{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-63888",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-63888"
  ],
  "published": "2026-07-19T14:56:29Z",
  "summary": "scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()\n\nTwo latent bugs in the Text-phase handler, both present since the\noriginal LIO integration in commit e48354ce078c (\"iscsi-target: Add\niSCSI fabric support for target v4.1\"):\n\n1) DataDigest CRC buffer overread (4 bytes past text_in).\n\n   text_in is kzalloc()'d at ALIGN(payload_length, 4).  rx_size is then\n   incremented by ISCSI_CRC_LEN to make room for the received DataDigest\n   in the iovec, but the same (now-bumped) rx_size is passed as the\n   buffer length to iscsit_crc_buf():\n\n       if (conn->conn_ops->DataDigest) {\n               ...\n               rx_size += ISCSI_CRC_LEN;\n       }\n       ...\n       if (conn->conn_ops->DataDigest) {\n               data_crc = iscsit_crc_buf(text_in, rx_size, 0, NULL);\n\n   iscsit_crc_buf() walks rx_size bytes of text_in with crc32c(), so\n   when DataDigest is negotiated it reads 4 bytes past the end of the\n   text_in allocation.  KASAN reproduces this directly on the unpatched\n   mainline tree as slab-out-of-bounds in crc32c() called from the Text\n   PDU path.  The OOB bytes feed crc32c() and are then compared against\n   the initiator-supplied checksum, so the value does not flow back to\n   the attacker, but the kernel does read past the buffer on every Text\n   PDU with DataDigest=CRC32C.\n\n   Fix by passing the actual padded payload length\n   (ALIGN(payload_length, 4)) that was used for the kzalloc().\n\n2) Stale cmd->text_in_ptr re-free (double-free) on ERL>0 bad DataDigest\n   drop.\n\n   On DataDigest mismatch with ErrorRecoveryLevel > 0 the handler\n   silently drops the PDU and lets the initiator plug the CmdSN gap:\n\n               kfree(text_in);\n               return 0;\n\n   cmd->text_in_ptr still points at the freed buffer.  The next Text\n   Request on the same ITT re-enters iscsit_setup_text_cmd(), which\n   unconditionally does\n\n       kfree(cmd->text_in_ptr);\n       cmd->text_in_ptr = NULL;\n\n   freeing the same pointer a second time.  Session teardown via\n   iscsit_release_cmd() has the same shape and hits the same double-free\n   if the connection is dropped before a second Text Request arrives.\n\n   On an unmodified mainline tree the bug-1 CRC overread fires first on\n   the initial valid Text Request and perturbs the subsequent state, so\n   #4 was isolated by building a kernel with only the bug-1 hunk of this\n   patch applied plus temporary printk() observability around the three\n   relevant kfree() sites.  The observability prints are not part of\n   this patch.  On that build, a three-PDU Text Request sequence after\n   login produces two back-to-back splats:\n\n       BUG: KASAN: double-free in iscsit_setup_text_cmd+0x??\n       BUG: KASAN: double-free in iscsit_release_cmd+0x??\n\n   showing the same pointer freed in the ERL>0 drop path and again in\n   iscsit_setup_text_cmd() (next Text Request on the same ITT) and once\n   more in iscsit_release_cmd() (session teardown).  On distro kernels\n   with CONFIG_SLAB_FREELIST_HARDENED=y (default) the double-free\n   becomes a remote kernel BUG(); on non-hardened kernels it corrupts\n   the slab freelist.\n\n   Fix by clearing cmd->text_in_ptr after the kfree() in the ERL>0 drop\n   path.  With both hunks applied #4 is directly observable on the stock\n   tree without observability printks; fixing bug-1 alone would mask #4\n   less, not more, so the hunks are submitted together.\n\nBoth fixes are one-liners.  The Text PDU state machine is unchanged and\nthe wire protocol is unaffected.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.176",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63888"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f7948af0dd03de84079dcd4dc215a69fd6fbb95d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/badf178b76b0690851df00f4ca9cf2eb8eb0f963"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6e22a1cdcc8277af4acc43710577157b77a02c5d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d3e9b79aa794f7a23e82de4d710e7d2df610e349"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ec9f19d52074a191ed1756ed4a7d39fff1a2085c"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/89c81d1228c00fa6dd91de6c1c5aa1ef8a7875e3"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5118ea225fe63b44207ba88047e4866e1ea43812"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/778c2ab142c625a8a8afa570e0f9b7873f445d99"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 9.8,
      "cvss_v3_severity": "Critical",
      "scenario": "AV:N - The bug is in the in-kernel LIO iSCSI target, reachable by sending iSCSI Text PDUs over TCP after connection setup on the network-facing iSCSI portal (typically port 3260), analogous to nfsd/ksmbd network exposure.\nAC:L - An attacker fully controls login parameter negotiation (DataDigest=CRC32C) and subsequent Text PDU content; the CRC overread fires deterministically on every qualifying Text PDU, and the double-free is reliably triggered by sending a bad DataDigest followed by another Text PDU on the same ITT when ERL>0.\nPR:N - No Linux OS privileges are required; the default discovery session permits unauthenticated login (AuthMethod=None, authentication disabled), after which SendTargets Text requests reach the vulnerable handler without any credentials.\nUI:N - Exploitation requires only crafted iSCSI protocol traffic from the attacker; no victim user action such as mounting a filesystem or clicking a link is needed.\nS:U - The vulnerability corrupts kernel heap memory within the iSCSI target subsystem on the host; it does not cross a VM, container, or IOMMU security boundary.\nC:H - The CRC path performs a slab out-of-bounds read past the text_in allocation, and the double-free is a use-after-free class bug that reads freed heap metadata; per kernel guidance both OOB reads and UAFs warrant High confidentiality impact.\nI:H - The double-free corrupts the slab freelist (triggering CONFIG_SLAB_FREELIST_HARDENED BUG() on hardened kernels), providing a classic heap corruption primitive that can be leveraged for arbitrary kernel memory writes and code execution.\nA:H - The double-free provably crashes the kernel (KASAN splat or SLAB_FREELIST_HARDENED BUG()), and the heap corruption can cause kernel panics; any UAF is scored as High availability impact per kernel guidance."
    }
  }
}