Skip to content
Heist/ feed
UnratedFix available

mctp: serial: handle zero-length frames to prevent rx buffer overflow

Type: advisorySource: OSV1 source record

In the Linux kernel, the following vulnerability has been resolved: mctp: serial: handle zero-length frames to prevent rx buffer overflow The MCTP serial receive state machine reads a frame length byte in mctp_serial_push_header() case 2 and validates it upper-bound-only: if (c > MCTP_SERIAL_FRAME_MTU) { dev->rxstate = STATE_ERR; } else { dev->rxlen = c; dev->rxpos = 0; dev->rxstate = STATE_DATA; ... } A length of zero passes this check, so rxlen is set to 0 and the state machine advances to STATE_DATA. In mctp_serial_push() STATE_DATA, the incoming byte is stored and rxpos incremented before the terminator is dev->rxbuf[dev->rxpos] = c; dev->rxpos++; dev->rxstate = STATE_DATA; if (dev->rxpos == dev->rxlen) { dev->rxpos = 0; dev->rxstate = STATE_TRAILER; } With rxlen == 0 the "rxpos == rxlen" terminator can never fire (rxpos is already 1 on the first data byte), so subsequent bytes are written past the end of the fixed 74-byte rxbuf, which is the last member of the netdev private area. Every following data byte is an attacker-controlled 1-byte out-of-bounds heap write, and the overflow continues until a frame (0x7e) or escape byte resets the parser -- effectively unbounded. Reaching this requires CAP_NET_ADMIN to attach the N_MCTP line discipline and bring the resulting mctpserialN netdev up, after which the bytes arrive via the tty receive path. Route a zero-length frame straight to STATE_TRAILER instead of STATE_DATA. The trailer/framing bytes are still consumed, and the fr

Announced Source revision 1
Original source ↗

CVE-2026-68124

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:CVE-2026-68124

Kernel

Source reference: /affected/1/package/name

Affected versions
Not stated in this record
Fixed versions
6.1.183

Source reference: /affected/1/ranges

6.6.148

Source reference: /affected/1/ranges

6.12.101

Source reference: /affected/1/ranges

6.18.42

Source reference: /affected/1/ranges

7.1.6

Source reference: /affected/1/ranges

Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
        "type": "GIT",
        "events": [
          {
            "introduced": "a0c2ccd9b5ad0a9e838158404e041b5a8ff762dd"
          },
          {
            "fixed": "64b96ae7912244d55257aa330d9569ee0a8f8d99"
          },
          {
            "fixed": "36dc6d6964a3b90411cc7944cd9b8b6f67b9807b"
          },
          {
            "fixed": "68819427bc07eca7963a9e8be19e5272cc29186c"
          },
          {
            "fixed": "f80ba170d7b3a44e3d244a2c8e06031d61bf3b23"
          },
          {
            "fixed": "06a6b606129c8a25cd457760f5370f3ff01fe05d"
          },
          {
            "fixed": "793b9b729f1e8de57be8c8daf1a9838be96cabed"
          }
        ]
      }
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68124.json"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "5.17.0"
          },
          {
            "fixed": "6.1.183"
          }
        ]
      },
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "6.2.0"
          },
          {
            "fixed": "6.6.148"
          }
        ]
      },
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "6.7.0"
          },
          {
            "fixed": "6.12.101"
          }
        ]
      },
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "6.13.0"
          },
          {
            "fixed": "6.18.42"
          }
        ]
      },
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "6.19.0"
          },
          {
            "fixed": "7.1.6"
          }
        ]
      }
    ],
    "package": {
      "name": "Kernel",
      "ecosystem": "Linux"
    },
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68124.json"
    }
  }
]
Related CVEs
CVE-2026-68124

Source reference: /id

Publisher severity

No explicit severity was provided.

Event
#50815 · Revision 1
Added to Heist Feed
Publisher date
Read the original announcement