Vulnerability-Lookup

GHSA-HCC6-6437-VWM2

Vulnerability from github – Published: 2025-12-08 03:31 – Updated: 2026-07-30 06:32

Details

In the Linux kernel, the following vulnerability has been resolved:

fbdev: bitblit: bound-check glyph index in bit_putcs*

bit_putcs_aligned()/unaligned() derived the glyph pointer from the character value masked by 0xff/0x1ff, which may exceed the actual font's glyph count and read past the end of the built-in font array. Clamp the index to the actual glyph count before computing the address.

This fixes a global out-of-bounds read reported by syzbot.

Severity

7.1 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2025-40322"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-12-08T01:16:04Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: bitblit: bound-check glyph index in bit_putcs*\n\nbit_putcs_aligned()/unaligned() derived the glyph pointer from the\ncharacter value masked by 0xff/0x1ff, which may exceed the actual font\u0027s\nglyph count and read past the end of the built-in font array.\nClamp the index to the actual glyph count before computing the address.\n\nThis fixes a global out-of-bounds read reported by syzbot.",
  "id": "GHSA-hcc6-6437-vwm2",
  "modified": "2026-07-30T06:32:23Z",
  "published": "2025-12-08T03:31:01Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40322"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0998a6cb232674408a03e8561dc15aa266b2f53b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/18c4ef4e765a798b47980555ed665d78b71aeadf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/901f44227072be60812fe8083e83e1533c04eed1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9ba1a7802ca9a2590cef95b253e6526f4364477f"
    },
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      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a10cede006f9614b465cf25609a8753efbfd45cc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c12003bf91fdff381c55ef54fef3e961a5af2545"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/db5c9a162d2f42bcc842b76b3d935dcc050a0eec"
    },
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      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/efaf89a75a29b2d179bf4fe63ca62852e93ad620"
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  "severity": [
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      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-40322 (GCVE-0-2025-40322)

Vulnerability from cvelistv5 – Published: 2025-12-08 00:46 – Updated: 2026-08-05 12:09

Title

fbdev: bitblit: bound-check glyph index in bit_putcs*

Summary

In the Linux kernel, the following vulnerability has been resolved: fbdev: bitblit: bound-check glyph index in bit_putcs* bit_putcs_aligned()/unaligned() derived the glyph pointer from the character value masked by 0xff/0x1ff, which may exceed the actual font's glyph count and read past the end of the built-in font array. Clamp the index to the actual glyph count before computing the address. This fixes a global out-of-bounds read reported by syzbot.

Severity

7.1 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-16 19:33 UTC

Assigner

Linux mitre root

References

8 references

URL	Tags
https://git.kernel.org/stable/c/a10cede006f9614b4…
https://git.kernel.org/stable/c/0998a6cb232674408…
https://git.kernel.org/stable/c/db5c9a162d2f42bcc…
https://git.kernel.org/stable/c/c12003bf91fdff381…
https://git.kernel.org/stable/c/9ba1a7802ca9a2590…
https://git.kernel.org/stable/c/901f44227072be608…
https://git.kernel.org/stable/c/efaf89a75a29b2d17…
https://git.kernel.org/stable/c/18c4ef4e765a798b4…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < a10cede006f9614b465cf25609a8753efbfd45cc (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 0998a6cb232674408a03e8561dc15aa266b2f53b (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < db5c9a162d2f42bcc842b76b3d935dcc050a0eec (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < c12003bf91fdff381c55ef54fef3e961a5af2545 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 9ba1a7802ca9a2590cef95b253e6526f4364477f (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 901f44227072be60812fe8083e83e1533c04eed1 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < efaf89a75a29b2d179bf4fe63ca62852e93ad620 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 18c4ef4e765a798b47980555ed665d78b71aeadf (git)
Linux	Linux	Affected: 2.6.12 Unaffected: 0 , < 2.6.12 (semver) Unaffected: 5.4.302 , ≤ 5.4.* (semver) Unaffected: 5.10.247 , ≤ 5.10.* (semver) Unaffected: 5.15.197 , ≤ 5.15.* (semver) Unaffected: 6.1.159 , ≤ 6.1.* (semver) Unaffected: 6.6.117 , ≤ 6.6.* (semver) Unaffected: 6.12.58 , ≤ 6.12.* (semver) Unaffected: 6.17.8 , ≤ 6.17.* (semver) Unaffected: 6.18 , ≤ * (original_commit_for_fix)

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{
  "containers": {
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                "id": "CVE-2025-40322",
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                "role": "CISA Coordinator",
                "timestamp": "2026-06-16T19:33:40.857434Z",
                "version": "2.0.3"
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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              "versionType": "git"
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              "version": "2.6.12"
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              "version": "0",
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            "version": "3.1"
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            {
              "lang": "en",
              "value": "AV:L - The vulnerable render path is reached only through local interfaces \u2014 `KDFONTOP` ioctl on a VT plus writes to `/dev/vcsa*` or the tty itself. There is no remote or adjacent-network exposure of fbcon.\nAC:L - The attacker fully controls both the desync (choosing font dimensions that make `vc_do_resize()` fail deterministically via `new_screen_size \u003e KMALLOC_MAX_SIZE` or `!new_screen_size`) and the trigger (writing glyph indices 256\u2013511 into the screen buffer); syzbot has a working C reproducer.\nPR:L - `KDFONTOP(KD_FONT_OP_SET)` and `PIO_UNIMAP` only require `perm`, which is granted to any unprivileged user whose controlling tty is the VT (`current-\u003esignal-\u003etty == tty`) \u2014 no capability is needed, and `vcs_open()` performs no capability check at all.\nUI:N - The attacker performs the font ioctl and the console write entirely from its own process; no victim action or cooperation is needed.\nS:U - The out-of-bounds read stays within the kernel\u0027s own memory and the impact is confined to the kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Up to 256 glyph cells are read past the font array \u2014 4 KB beyond the global `fontdata_8x16`, or up to ~256 KB beyond a large user-supplied font \u2014 and those raw kernel bytes are blitted to the framebuffer as bitmaps that the attacker can read back via `/dev/fb0`, yielding a substantial kernel memory disclosure primitive.\nI:N - The defect is strictly an out-of-bounds read; the fetched bytes are copied into correctly sized pixmap and attribute buffers, so no kernel memory is modified and no write or control-flow primitive is produced.\nA:H - When the active font is a large kvmalloc-backed user font, the overrun can run hundreds of kilobytes past the allocation into a vmalloc guard page, faulting inside `bit_putcs()` while `console_lock` is held and oopsing/hanging the system; on KASAN builds it trips a report that can panic."
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}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

GHSA-HCC6-6437-VWM2

CVE-2025-40322 (GCVE-0-2025-40322)

Tags

Sightings

Nomenclature

Related by attack behaviour