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CVE Record

CVE-2025-40322: fbdev: bitblit: bound-check glyph index in bit_putcs*

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

A Linux kernel framebuffer text-rendering path could read past the end of a built-in font table. The public record describes a resolved kernel bug reported by syzbot. Business urgency is mainly for Linux fleets that still expose fbdev framebuffer console paths; there is no cited evidence of active exploitation.

Executive priority

Treat as a routine kernel remediation item unless fbdev console paths are broadly used in sensitive systems. Patch through normal Linux maintenance, with faster handling for exposed or safety-critical hosts.

Technical view

The issue is in fbdev bitblit bit_putcs_aligned()/bit_putcs_unaligned(). A character-derived glyph index was masked but not bounded against the actual font glyph count, allowing a global out-of-bounds read before the kernel fix clamps the index.

Likely exposure

Exposure is likely limited to Linux kernels with vulnerable fbdev bitblit/font rendering code reachable in the deployed configuration. The bundle lists Linux as affected and provides stable kernel fix commits, but it does not identify distributions, appliance products, or exploit prerequisites.

Exploitation context

The source bundle says syzbot reported a global out-of-bounds read. It does not cite public exploitation, weaponized proof of concept, or CISA KEV listing; KEV is false in the supplied data.

Researcher notes

Evidence supports an out-of-bounds read in fbdev glyph indexing fixed by bounds checking. The bundle lacks CVSS, CWE, exploitability detail, and distribution impact. Validate reachability in local configs before assigning higher operational urgency.

Mitigation direction

  • Update affected Linux kernels to vendor-supported builds containing the listed stable fixes.
  • Prioritize systems using framebuffer console or fbdev-related display paths.
  • Check Linux distribution advisories for backported fixes and package-specific status.
  • Avoid assuming version strings alone prove safety; confirm the exact patched build.
  • Track kernel.org stable commits listed in the CVE record.

Validation and detection

  • Inventory Linux kernel versions and vendor package releases across the fleet.
  • Check whether fbdev/framebuffer console support is enabled or required.
  • Map installed kernels to vendor advisories or the listed stable commits.
  • Review kernel logs and crash telemetry for framebuffer-related anomalies.
  • Confirm patched kernels boot and preserve required console/display behavior.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2025-40322 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
1ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 5.4.302, 5.10.247, 5.15.197, 6.1.159, 6.6.117, 6.12.58, 6.17.8, 6.18affected
Weakness

CWE details

No CWE listed

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