FKIE_CVE-2026-63949

Vulnerability from fkie_nvd - Published: 2026-07-19 16:17 - Updated: 2026-07-19 16:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: auxdisplay: line-display: fix OOB read on zero-length message_store() linedisp_display() unconditionally reads msg[count - 1] before checking whether count is zero, so a write of zero bytes to the message sysfs attribute hits msg[-1]: write(fd, "", 0); -> message_store(..., buf, count=0) -> linedisp_display(linedisp, buf, count=0) -> msg[count - 1] == '\n' ; OOB read The kernfs write buffer for that store is a 1-byte allocation (kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0), so msg[-1] is a 1-byte read before the slab object. On a KASAN-enabled kernel this trips an out-of-bounds report and panics; on stock kernels it silently reads adjacent slab data and, if that byte happens to be '\n', the following count-- wraps ssize_t 0 to -1 and is then passed to kmemdup_nul(). linedisp_display() is reached from the message_store() sysfs callback (drivers/auxdisplay/line-display.c message attribute, mode 0644) and from the in-tree initial-message setup with count == -1, so the OOB path is only userspace-triggerable via zero-byte writes; vfs_write() does not short-circuit on count == 0 and kernfs_fop_write_iter() dispatches the store callback regardless. Guard the trailing-newline trim with a count check. The existing if (!count) block then takes the clear-display path unchanged. Affects every auxdisplay driver that registers via linedisp_register() / linedisp_attach(): ht16k33, max6959, img-ascii-lcd, seg-led-gpio.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/auxdisplay/line-display.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ca5b0781946d5083ceafa752141f47f085853620",
              "status": "affected",
              "version": "7e76aece6f036cb7ada4858d6aa73825bfe22983",
              "versionType": "git"
            },
            {
              "lessThan": "8776032fe989a9b5fc77f2de5e03e4adb44c630e",
              "status": "affected",
              "version": "7e76aece6f036cb7ada4858d6aa73825bfe22983",
              "versionType": "git"
            },
            {
              "lessThan": "3859960daeb9b7b39b9847b5b0113bc6081eb735",
              "status": "affected",
              "version": "7e76aece6f036cb7ada4858d6aa73825bfe22983",
              "versionType": "git"
            },
            {
              "lessThan": "197476b126010bac1b3199833c6966cd6f54c2a9",
              "status": "affected",
              "version": "7e76aece6f036cb7ada4858d6aa73825bfe22983",
              "versionType": "git"
            },
            {
              "lessThan": "6ad4f75ef9f3372fce8cad494e789ac6a5507bef",
              "status": "affected",
              "version": "7e76aece6f036cb7ada4858d6aa73825bfe22983",
              "versionType": "git"
            },
            {
              "lessThan": "a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6",
              "status": "affected",
              "version": "7e76aece6f036cb7ada4858d6aa73825bfe22983",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/auxdisplay/line-display.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.16"
            },
            {
              "lessThan": "5.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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] == \u0027\\n\u0027  ; 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 \u0027\\n\u0027, 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",
  "lastModified": "2026-07-19T16:17:13.600",
  "metrics": {},
  "published": "2026-07-19T16:17:13.600",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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