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CVE-2021-47383 (GCVE-0-2021-47383)

Vulnerability from cvelistv5 – Published: 2024-05-21 15:03 – Updated: 2026-08-05 08:47
VLAI
Title
tty: Fix out-of-bound vmalloc access in imageblit
Summary
In the Linux kernel, the following vulnerability has been resolved: tty: Fix out-of-bound vmalloc access in imageblit This issue happens when a userspace program does an ioctl FBIOPUT_VSCREENINFO passing the fb_var_screeninfo struct containing only the fields xres, yres, and bits_per_pixel with values. If this struct is the same as the previous ioctl, the vc_resize() detects it and doesn't call the resize_screen(), leaving the fb_var_screeninfo incomplete. And this leads to the updatescrollmode() calculates a wrong value to fbcon_display->vrows, which makes the real_y() return a wrong value of y, and that value, eventually, causes the imageblit to access an out-of-bound address value. To solve this issue I made the resize_screen() be called even if the screen does not need any resizing, so it will "fix and fill" the fb_var_screeninfo independently.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-06-17 17:37 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7e71fcedfda6f7de18f850a6b36e78d78b04476f (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 70aed03b1d5a5df974f456cdc8eedb213c94bb8b (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 067c694d06040db6f0c65281bb358452ca6d85b9 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8a6a240f52e14356386030d8958ae8b1761d2325 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 883f7897a25e3ce14a7f274ca4c73f49ac84002a (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d570c48dd37dbe8fc6875d4461d01a9554ae2560 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 699d926585daa6ec44be556cdc1ab89e5d54557b (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 3b0c406124719b625b1aba431659f5cdc24a982c (git)
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Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 4.4.286 , ≤ 4.4.* (semver)
Unaffected: 4.9.285 , ≤ 4.9.* (semver)
Unaffected: 4.14.249 , ≤ 4.14.* (semver)
Unaffected: 4.19.209 , ≤ 4.19.* (semver)
Unaffected: 5.4.151 , ≤ 5.4.* (semver)
Unaffected: 5.10.71 , ≤ 5.10.* (semver)
Unaffected: 5.14.10 , ≤ 5.14.* (semver)
Unaffected: 5.15 , ≤ * (original_commit_for_fix)
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And this leads to\\nthe updatescrollmode() calculates a wrong value to\\nfbcon_display-\u003evrows, which makes the real_y() return a\\nwrong value of y, and that value, eventually, causes\\nthe imageblit to access an out-of-bound address value.\\n\\nTo solve this issue I made the resize_screen() be called\\neven if the screen does not need any resizing, so it will\\n\\\"fix and fill\\\" the fb_var_screeninfo independently.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: tty: corrige el acceso vmalloc fuera de los l\u00edmites en imageblit. Este problema ocurre cuando un programa de espacio de usuario realiza un ioctl FBIOPUT_VSCREENINFO pasando la estructura fb_var_screeninfo que contiene solo los campos xres, yres y bits_per_pixel con valores. Si esta estructura es la misma que la ioctl anterior, vc_resize() la detecta y no llama a resize_screen(), dejando fb_var_screeninfo incompleto. Y esto lleva a que updatecrollmode() calcule un valor incorrecto para fbcon_display-\u0026gt;vrows, lo que hace que real_y() devuelva un valor incorrecto de y, y ese valor, eventualmente, hace que imageblit acceda a un valor de direcci\u00f3n fuera de los l\u00edmites. . Para resolver este problema, hice que se llamara a resize_screen() incluso si la pantalla no necesita ning\u00fan cambio de tama\u00f1o, por lo que \\\"arreglar\u00e1 y completar\u00e1\\\" fb_var_screeninfo de forma 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:57:45+00:00",
      "cve": "CVE-2021-47383",
      "id": "CVE-2021-47383",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:fixed": "664",
      "product_status:known_affected": "50",
      "product_status:known_not_affected": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tty: Fix out-of-bound vmalloc access in imageblit",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47383.json",
      "version": "3"
    },
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      "cveMetadata": "{\"cveId\": \"CVE-2021-47383\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:47:33.469Z\", \"dateReserved\": \"2024-05-21T14:58:30.812Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-21T15:03:44.286Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.