{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "7e76aece6f036cb7ada4858d6aa73825bfe22983"
            },
            {
              "fixed": "ca5b0781946d5083ceafa752141f47f085853620"
            },
            {
              "fixed": "8776032fe989a9b5fc77f2de5e03e4adb44c630e"
            },
            {
              "fixed": "3859960daeb9b7b39b9847b5b0113bc6081eb735"
            },
            {
              "fixed": "197476b126010bac1b3199833c6966cd6f54c2a9"
            },
            {
              "fixed": "6ad4f75ef9f3372fce8cad494e789ac6a5507bef"
            },
            {
              "fixed": "a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "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-2026-63949.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nauxdisplay: line-display: fix OOB read on zero-length message_store()\n\nlinedisp_display() unconditionally reads msg[count - 1] before\nchecking whether count is zero, so a write of zero bytes to the\nmessage sysfs attribute hits msg[-1]:\n\n\twrite(fd, \"\", 0);\n\n\t-\u003e message_store(..., buf, count=0)\n\t   -\u003e linedisp_display(linedisp, buf, count=0)\n\t      -\u003e msg[count - 1] == '\\n'  ; OOB read\n\nThe kernfs write buffer for that store is a 1-byte allocation\n(kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0),\nso msg[-1] is a 1-byte read before the slab object. On a\nKASAN-enabled kernel this trips an out-of-bounds report and\npanics; on stock kernels it silently reads adjacent slab data\nand, if that byte happens to be '\\n', the following count--\nwraps ssize_t 0 to -1 and is then passed to kmemdup_nul().\n\nlinedisp_display() is reached from the message_store() sysfs\ncallback (drivers/auxdisplay/line-display.c message attribute,\nmode 0644) and from the in-tree initial-message setup with\ncount == -1, so the OOB path is only userspace-triggerable via\nzero-byte writes; vfs_write() does not short-circuit on\ncount == 0 and kernfs_fop_write_iter() dispatches the store\ncallback regardless.\n\nGuard the trailing-newline trim with a count check. The\nexisting if (!count) block then takes the clear-display path\nunchanged.\n\nAffects every auxdisplay driver that registers via\nlinedisp_register() / linedisp_attach(): ht16k33, max6959,\nimg-ascii-lcd, seg-led-gpio.",
  "id": "CVE-2026-63949",
  "modified": "2026-07-21T03:41:45.062026901Z",
  "published": "2026-07-19T14:55:42.679Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63949.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63949"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.8.0",
  "summary": "auxdisplay: line-display: fix OOB read on zero-length message_store()"
}