CVE-2025-40322Public exploit

Kernel memory disclosure and hang via glyph overread

Published Dec 8, 2025 · Updated Aug 5, 2026

An out-of-bounds read in Linux kernel fbdev bitblit allows local users to disclose kernel memory or hang the system. The bit_putcs_aligned() and bit_putcs_unaligned() paths mask each character value to 0xff or 0x1ff and use the result as a glyph index without checking the active font's actual glyph count. A low-privileged user controlling a virtual terminal can desynchronize font dimensions, write glyph indices 256–511, and render out-of-range kernel bytes to the framebuffer; a large user font can instead fault while the console lock is held.

CVSS severity7.1
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An out-of-bounds read in Linux kernel fbdev bitblit allows local users to disclose kernel memory or hang the system. The bit_putcs_aligned() and bit_putcs_unaligned() paths mask each character value to 0xff or 0x1ff and use the result as a glyph index without checking the active font's actual glyph count. A low-privileged user controlling a virtual terminal can desynchronize font dimensions, write glyph indices 256–511, and render out-of-range kernel bytes to the framebuffer; a large user font can instead fault while the console lock is held.

The record

CVE
CVE-2025-40322
Published
Dec 8, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1005, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 8, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0998a6cb232674408a03e8561dc15aa266b2f53b
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <18c4ef4e765a798b47980555ed665d78b71aeadf
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <901f44227072be60812fe8083e83e1533c04eed1
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9ba1a7802ca9a2590cef95b253e6526f4364477f
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a10cede006f9614b465cf25609a8753efbfd45cc
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c12003bf91fdff381c55ef54fef3e961a5af2545
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <db5c9a162d2f42bcc842b76b3d935dcc050a0eec
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <efaf89a75a29b2d179bf4fe63ca62852e93ad620
  9. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0998a6cb232674408a03e8561dc15aa266b2f53b; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <18c4ef4e765a798b47980555ed665d78b71aeadf; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <901f44227072be60812fe8083e83e1533c04eed1; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9ba1a7802ca9a2590cef95b253e6526f4364477f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a10cede006f9614b465cf25609a8753efbfd45cc; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c12003bf91fdff381c55ef54fef3e961a5af2545; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <db5c9a162d2f42bcc842b76b3d935dcc050a0eec; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <efaf89a75a29b2d179bf4fe63ca62852e93ad620; version=2.6.12

Published CVSS scores

7.1LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1005Data from Local System
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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