FKIE_CVE-2026-53402

Vulnerability from fkie_nvd - Published: 2026-07-19 12:16 - Updated: 2026-07-20 15:16
Severity
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() When fbcon_do_set_font() fails (e.g., due to a memory allocation failure inside vc_resize() under heavy memory pressure), it jumps to the `err_out` label to roll back the console state. However, the current rollback logic forgets to restore the `hi_font` state, leading to a severe state machine corruption. Earlier in the function, `set_vc_hi_font()` might be called to change `vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()` subsequently fails, the `err_out` path restores `vc_font.charcount` but entirely skips rolling back the `vc_hi_font_mask` and the screen buffer. This mismatch leaves the terminal in a desynchronized state. Because `vc_hi_font_mask` remains set, the VT subsystem will still accept character indices greater than 255 from userspace and write them to the screen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will then use these inflated indices to access the reverted, 256-character font array, leading to a deterministic out-of-bounds read and potential kernel memory disclosure. Fix this by adding the missing rollback logic for the `hi_font` mask and screen buffer in the error path.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/076b1aa65f77a49bce5a48a4a55a397cfcafa2b8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/39815715cbcfabb16fc8c5f4a23deeda20f5df62
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b5bb2c696e140c399cb874def2feedf61dee27d6
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/video/fbdev/core/fbcon.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b5bb2c696e140c399cb874def2feedf61dee27d6",
              "status": "affected",
              "version": "a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24",
              "versionType": "git"
            },
            {
              "lessThan": "076b1aa65f77a49bce5a48a4a55a397cfcafa2b8",
              "status": "affected",
              "version": "a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24",
              "versionType": "git"
            },
            {
              "lessThan": "39815715cbcfabb16fc8c5f4a23deeda20f5df62",
              "status": "affected",
              "version": "a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24",
              "versionType": "git"
            },
            {
              "lessThan": "8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2",
              "status": "affected",
              "version": "a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "868749a7456dc48e93887a8474194e2ee6d6c21f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ebd6f886aa2447fcfcdce5450c9e1028e1d681bb",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "f08ccb792d3eaf1dc62d8cbf6a30d6522329f660",
              "versionType": "git"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.249",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.64",
              "versionType": "semver"
            },
            {
              "lessThan": "5.20",
              "status": "affected",
              "version": "5.19.6",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/video/fbdev/core/fbcon.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.0"
            },
            {
              "lessThan": "6.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.96",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "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\nfbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()\n\nWhen fbcon_do_set_font() fails (e.g., due to a memory allocation failure\ninside vc_resize() under heavy memory pressure), it jumps to the `err_out`\nlabel to roll back the console state. However, the current rollback logic\nforgets to restore the `hi_font` state, leading to a severe state machine\ncorruption.\n\nEarlier in the function, `set_vc_hi_font()` might be called to change\n`vc-\u003evc_hi_font_mask` and mutate the screen buffer. If `vc_resize()`\nsubsequently fails, the `err_out` path restores `vc_font.charcount`\nbut entirely skips rolling back the `vc_hi_font_mask` and the screen\nbuffer.\n\nThis mismatch leaves the terminal in a desynchronized state. Because\n`vc_hi_font_mask` remains set, the VT subsystem will still accept\ncharacter indices greater than 255 from userspace and write them to the\nscreen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will\nthen use these inflated indices to access the reverted, 256-character\nfont array, leading to a deterministic out-of-bounds read and potential\nkernel memory disclosure.\n\nFix this by adding the missing rollback logic for the `hi_font` mask\nand screen buffer in the error path."
    }
  ],
  "id": "CVE-2026-53402",
  "lastModified": "2026-07-20T15:16:42.863",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.1,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.2,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T12:16:51.387",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/076b1aa65f77a49bce5a48a4a55a397cfcafa2b8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/39815715cbcfabb16fc8c5f4a23deeda20f5df62"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b5bb2c696e140c399cb874def2feedf61dee27d6"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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