{ "affected": [ { "ranges": [ { "events": [ { "introduced": "e48354ce078c079996f89d715dfa44814b4eba01" }, { "fixed": "f7948af0dd03de84079dcd4dc215a69fd6fbb95d" }, { "fixed": "badf178b76b0690851df00f4ca9cf2eb8eb0f963" }, { "fixed": "6e22a1cdcc8277af4acc43710577157b77a02c5d" }, { "fixed": "d3e9b79aa794f7a23e82de4d710e7d2df610e349" }, { "fixed": "ec9f19d52074a191ed1756ed4a7d39fff1a2085c" }, { "fixed": "89c81d1228c00fa6dd91de6c1c5aa1ef8a7875e3" }, { "fixed": "5118ea225fe63b44207ba88047e4866e1ea43812" }, { "fixed": "778c2ab142c625a8a8afa570e0f9b7873f445d99" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" } ] }, { "package": { "ecosystem": "Linux", "name": "Kernel" }, "ranges": [ { "events": [ { "introduced": "3.1.0" }, { "fixed": "5.10.259" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.11.0" }, { "fixed": "5.15.210" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.16.0" }, { "fixed": "6.1.176" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.2.0" }, { "fixed": "6.6.143" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.7.0" }, { "fixed": "6.12.93" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.13.0" }, { "fixed": "6.18.35" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.19.0" }, { "fixed": "7.0.12" } ], "type": "ECOSYSTEM" } ] } ], "database_specific": { "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63888.json" }, "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-\u003econn_ops-\u003eDataDigest) {\n ...\n rx_size += ISCSI_CRC_LEN;\n }\n ...\n if (conn-\u003econn_ops-\u003eDataDigest) {\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-\u003etext_in_ptr re-free (double-free) on ERL\u003e0 bad DataDigest\n drop.\n\n On DataDigest mismatch with ErrorRecoveryLevel \u003e 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-\u003etext_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-\u003etext_in_ptr);\n cmd-\u003etext_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\u003e0 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-\u003etext_in_ptr after the kfree() in the ERL\u003e0 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.", "id": "CVE-2026-63888", "modified": "2026-07-21T03:42:15.008473162Z", "published": "2026-07-19T14:55:00.803Z", "references": [ { "type": "WEB", "url": "https://git.kernel.org/stable/c/5118ea225fe63b44207ba88047e4866e1ea43812" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/6e22a1cdcc8277af4acc43710577157b77a02c5d" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/778c2ab142c625a8a8afa570e0f9b7873f445d99" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/89c81d1228c00fa6dd91de6c1c5aa1ef8a7875e3" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/badf178b76b0690851df00f4ca9cf2eb8eb0f963" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/d3e9b79aa794f7a23e82de4d710e7d2df610e349" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/ec9f19d52074a191ed1756ed4a7d39fff1a2085c" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/f7948af0dd03de84079dcd4dc215a69fd6fbb95d" }, { "type": "ADVISORY", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63888.json" }, { "type": "ADVISORY", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63888" }, { "type": "PACKAGE", "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git" } ], "schema_version": "1.8.0", "severity": [ { "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "type": "CVSS_V3" } ], "summary": "scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()" }