CVE-2026-80578 (GCVE-0-2026-80578)

Vulnerability from cvelistv5 – Published: 2026-08-26 14:37 – Updated: 2026-08-27 05:01
VLAI
Title
fbdev: core: Fix pointer desynchronization in fb_io_read()
Summary
In the Linux kernel, the following vulnerability has been resolved: fbdev: core: Fix pointer desynchronization in fb_io_read() In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to a faulty user buffer), the loop adjusts the chunk size 'c' and updates the remaining 'count'. However, the hardware 'src' pointer has already been eagerly advanced by the original chunk size. If the loop is allowed to continue, the read will resume from an incorrect, over-advanced offset. Since the remaining 'count' was only decremented by the successful bytes, this desynchronization causes the next iterations to execute more hardware reads than originally bounded, eventually leading to out-of-bounds I/O reads. Fix this by breaking out of the loop immediately upon a partial copy_to_user(). A partial copy indicates a faulty user buffer, making subsequent read attempts futile. Breaking out ensures we return the number of successfully read bytes without risking out-of-bounds hardware accesses in subsequent mismatched iterations.
Severity
7.3 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff , < 42bc07b4e5a3c8a02a433388f562a8f46d093e11 (git)
Affected: 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff , < 42a6d8126c194133eafab2b0fd5c8668ebfcba5b (git)
Affected: 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff , < 7ff87a01ae3a8cd0208f7499386998223a8b5dba (git)
Affected: 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff , < 7110b7b794a2aac2c5cf8eb06ebf2af724c74d50 (git)
Affected: 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff , < 81cc73be40c6f028f1ee3f438ace46afe666dbae (git)
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Linux Linux Affected: 6.5
Unaffected: 0 , < 6.5 (semver)
Unaffected: 6.6.153 , ≤ 6.6.* (semver)
Unaffected: 6.12.105 , ≤ 6.12.* (semver)
Unaffected: 6.18.46 , ≤ 6.18.* (semver)
Unaffected: 7.1.10 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/video/fbdev/core/fb_io_fops.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "status": "unaffected",
              "version": "6.18.46",
              "versionType": "semver"
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              "version": "7.1.10",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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        }
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: core: Fix pointer desynchronization in fb_io_read()\n\nIn fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to\na faulty user buffer), the loop adjusts the chunk size \u0027c\u0027 and updates\nthe remaining \u0027count\u0027. However, the hardware \u0027src\u0027 pointer has already\nbeen eagerly advanced by the original chunk size.\n\nIf the loop is allowed to continue, the read will resume from an\nincorrect, over-advanced offset. Since the remaining \u0027count\u0027 was only\ndecremented by the successful bytes, this desynchronization causes the\nnext iterations to execute more hardware reads than originally bounded,\neventually leading to out-of-bounds I/O reads.\n\nFix this by breaking out of the loop immediately upon a partial\ncopy_to_user(). A partial copy indicates a faulty user buffer, making\nsubsequent read attempts futile. Breaking out ensures we return the\nnumber of successfully read bytes without risking out-of-bounds hardware\naccesses in subsequent mismatched iterations."
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            "version": "3.1"
          },
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              "value": "AV:L - Exploitation requires a local read(2) on /dev/fb* through fb_read() in fb_chrdev.c, which calls fb_io_read() for I/O-mapped framebuffers (efifb, simplefb, embedded/industrial LCD drivers); no network, adjacent-radio, or physical-bus handler reaches this code.\nAC:L - The attacker fully controls read offset, length, and user-buffer layout; mmap/mprotect can force a partial copy_to_user() at a page boundary on the first chunk, desynchronizing src without races, rare configs, or conditions outside attacker control.\nPR:L - Triggering requires only local permission to open /dev/fb* (video group, seat uaccess ACL, or default console user on embedded HMIs, kiosks, and automotive/industrial displays using I/O framebuffers); no CAP_SYS_ADMIN or init-namespace root is needed.\nUI:N - Once framebuffer access is available, the attacker triggers the bug solely via crafted read() calls from their own process; no victim, administrator, or other-user interaction is required.\nS:U - Impact is confined to the host kernel and MMIO regions behind the framebuffer mapping; it does not cross VM, container, or IOMMU boundaries into a separate security authority.\nC:H - Pointer desynchronization lets fb_memcpy_fromio() read past screen_size/smem_len into adjacent MMIO (GPU/display registers, firmware handoff data), copying that hardware memory into the attacker user buffer; out-of-bounds I/O read warrants High confidentiality impact.\nI:L - Out-of-bounds MMIO reads can hit read-sensitive device registers (clear-on-read, mode or DMA control fields), causing limited but real hardware/display state modification even though no direct arbitrary kernel-memory write primitive is provided.\nA:H - Repeated unbounded I/O reads beyond the mapped framebuffer can hang or reset display/GPU hardware, provoke bus errors or machine checks on some platforms, and fault on unmapped iomem leading to kernel oops or panic."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-08-27T05:01:59.582Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/42bc07b4e5a3c8a02a433388f562a8f46d093e11"
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          "url": "https://git.kernel.org/stable/c/42a6d8126c194133eafab2b0fd5c8668ebfcba5b"
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        },
        {
          "url": "https://git.kernel.org/stable/c/81cc73be40c6f028f1ee3f438ace46afe666dbae"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80578",
    "datePublished": "2026-08-26T14:37:36.722Z",
    "dateReserved": "2026-08-26T14:34:25.769Z",
    "dateUpdated": "2026-08-27T05:01:59.582Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-09-01",
      "epss": "0.00116",
      "percentile": "0.01801"
    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-27T11:15:30+00:00",
      "cve": "CVE-2026-80578",
      "id": "CVE-2026-80578",
      "initial_release_date": "2026-08-26T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: fbdev: core: Fix pointer desynchronization in fb_io_read()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80578.json",
      "version": "3"
    }
  }
}



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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.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • 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.