{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68124","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-30T09:28:09.369Z","datePublished":"2026-08-10T11:58:44.997Z","dateUpdated":"2026-08-19T16:29:36.851Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-19T16:29:36.851Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmctp: serial: handle zero-length frames to prevent rx buffer overflow\n\nThe MCTP serial receive state machine reads a frame length byte in\nmctp_serial_push_header() case 2 and validates it upper-bound-only:\n\n\tif (c > MCTP_SERIAL_FRAME_MTU) {\n\t\tdev->rxstate = STATE_ERR;\n\t} else {\n\t\tdev->rxlen = c;\n\t\tdev->rxpos = 0;\n\t\tdev->rxstate = STATE_DATA;\n\t\t...\n\t}\n\nA length of zero passes this check, so rxlen is set to 0 and the state\nmachine advances to STATE_DATA. In mctp_serial_push() STATE_DATA, the\nincoming byte is stored and rxpos incremented before the terminator is\n\n\tdev->rxbuf[dev->rxpos] = c;\n\tdev->rxpos++;\n\tdev->rxstate = STATE_DATA;\n\tif (dev->rxpos == dev->rxlen) {\n\t\tdev->rxpos = 0;\n\t\tdev->rxstate = STATE_TRAILER;\n\t}\n\nWith rxlen == 0 the \"rxpos == rxlen\" terminator can never fire (rxpos is\nalready 1 on the first data byte), so subsequent bytes are written past\nthe end of the fixed 74-byte rxbuf, which is the last member of the\nnetdev private area. Every following data byte is an attacker-controlled\n1-byte out-of-bounds heap write, and the overflow continues until a\nframe (0x7e) or escape byte resets the parser -- effectively unbounded.\n\nReaching this requires CAP_NET_ADMIN to attach the N_MCTP line\ndiscipline and bring the resulting mctpserialN netdev up, after which\nthe bytes arrive via the tty receive path.\n\nRoute a zero-length frame straight to STATE_TRAILER instead of\nSTATE_DATA. The trailer/framing bytes are still consumed, and the frame\nresolves to a zero-length skb that the MCTP core rejects; the parser\nnever enters STATE_DATA with rxlen == 0, so the out-of-bounds write can\nno longer occur.\n\nKASAN, on a frame of 0x7e 0x01 0x00 followed by data bytes (before this\nchange):\n\n  UBSAN: array-index-out-of-bounds in drivers/net/mctp/mctp-serial.c:370\n  index 74 is out of range for type 'u8 [74]'\n  BUG: KASAN: slab-out-of-bounds in mctp_serial_tty_receive_buf\n  Write of size 1 at addr ... by task kworker/u16:0\n   mctp_serial_tty_receive_buf\n   tty_ldisc_receive_buf\n   flush_to_ldisc\n  Allocated by task 152:\n   alloc_netdev_mqs\n   mctp_serial_open\n\nv2: route zero-length frames to STATE_TRAILER instead of STATE_ERR so\n    the trailer/framing bytes are still consumed (Jeremy Kerr).\n\nFound by 0sec automated security-research tooling (https://0sec.ai)."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":9.6,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:A - The bug is triggered in mctp_serial_tty_receive_buf() by crafted DSP0253 serial frames; on BMC/datacenter systems MCTP-over-serial links management controllers on a shared management LAN, letting an adjacent unauthenticated peer inject 0x7e/0x01/0x00 frames without using host syscalls.\nAC:L - Exploitation is deterministic: a zero-length length byte bypasses the upper-bound check, then each following serial byte is a controlled 1-byte heap OOB write until 0x7e/0x7d resets the parser; no races or attacker-uncontrollable memory layout are required.\nPR:N - Triggering the overflow only requires delivering malicious serial bytes to an already-configured, running mctpserial netdev; a remote/adjacent MCTP peer or compromised management controller needs no Linux host credentials, CAP_NET_ADMIN, or root on the victim.\nUI:N - No victim user action is required at exploit time; administrative enablement of MCTP serial is deployment configuration, not end-user interaction under CVSS.\nS:C - Kconfig documents virtio-serial VM interconnect for MCTP serial; a malicious guest sending crafted frames to the host-side mctpserial binding can corrupt host kernel heap memory, crossing the guest/host virtualization security boundary.\nC:H - Each overflow byte is attacker-controlled and the write stream is effectively unbounded past the 74-byte rxbuf (last netdev private field), enabling slab-out-of-bounds corruption that can be leveraged for arbitrary kernel memory disclosure.\nI:H - Sustained attacker-controlled out-of-bounds heap writes can corrupt adjacent kmalloc objects, function pointers, and netdev state, providing a standard path to arbitrary kernel write and privilege-escalating code execution.\nA:H - KASAN/UBSAN report slab-out-of-bounds and array-index-out-of-bounds in mctp_serial_tty_receive_buf via flush_to_ldisc; continued overflow reliably causes kernel oops/panic or hang during tty receive processing."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/mctp/mctp-serial.c"],"versions":[{"version":"a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd","lessThan":"64b96ae7912244d55257aa330d9569ee0a8f8d99","status":"affected","versionType":"git"},{"version":"a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd","lessThan":"36dc6d6964a3b90411cc7944cd9b8b6f67b9807b","status":"affected","versionType":"git"},{"version":"a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd","lessThan":"68819427bc07eca7963a9e8be19e5272cc29186c","status":"affected","versionType":"git"},{"version":"a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd","lessThan":"f80ba170d7b3a44e3d244a2c8e06031d61bf3b23","status":"affected","versionType":"git"},{"version":"a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd","lessThan":"06a6b606129c8a25cd457760f5370f3ff01fe05d","status":"affected","versionType":"git"},{"version":"a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd","lessThan":"793b9b729f1e8de57be8c8daf1a9838be96cabed","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/mctp/mctp-serial.c"],"versions":[{"version":"5.17","status":"affected"},{"version":"0","lessThan":"5.17","status":"unaffected","versionType":"semver"},{"version":"6.1.183","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.148","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.101","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.42","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.6","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.6.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.12.101"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/64b96ae7912244d55257aa330d9569ee0a8f8d99"},{"url":"https://git.kernel.org/stable/c/36dc6d6964a3b90411cc7944cd9b8b6f67b9807b"},{"url":"https://git.kernel.org/stable/c/68819427bc07eca7963a9e8be19e5272cc29186c"},{"url":"https://git.kernel.org/stable/c/f80ba170d7b3a44e3d244a2c8e06031d61bf3b23"},{"url":"https://git.kernel.org/stable/c/06a6b606129c8a25cd457760f5370f3ff01fe05d"},{"url":"https://git.kernel.org/stable/c/793b9b729f1e8de57be8c8daf1a9838be96cabed"}],"title":"mctp: serial: handle zero-length frames to prevent rx buffer overflow","x_generator":{"engine":"bippy-1.2.0"}}}}