Privileged kernel panic via zero-byte sysfs write
Published Jul 19, 2026 · Updated Jul 19, 2026
Out-of-bounds read in Linux Kernel allows local users with sysfs write access to panic KASAN-enabled systems via a zero-byte write. linedisp_display() reads msg[count - 1] before checking for a zero count; if the preceding slab byte is a newline, decrementing count wraps zero to -1 before kmemdup_nul(). The message attribute is mode 0644 and exists only when ht16k33, max6959, img-ascii-lcd, or seg-led-gpio registers the line display; stock kernels otherwise read one adjacent byte without exposing it directly.
Summary
What happened
Out-of-bounds read in Linux Kernel allows local users with sysfs write access to panic KASAN-enabled systems via a zero-byte write. linedisp_display() reads msg[count - 1] before checking for a zero count; if the preceding slab byte is a newline, decrementing count wraps zero to -1 before kmemdup_nul(). The message attribute is mode 0644 and exists only when ht16k33, max6959, img-ascii-lcd, or seg-led-gpio registers the line display; stock kernels otherwise read one adjacent byte without exposing it directly.
The record
- CVE
- CVE-2026-63949
- Published
- Jul 19, 2026
- Updated
- Jul 19, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- T1499
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Jul 19, 2026CVE publishedPublication date reported by the CVE source.
- Jul 19, 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?
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- Affected versionversion=5.16
- Affected versionversion=7e76aece6f036cb7ada4858d6aa73825bfe22983 <197476b126010bac1b3199833c6966cd6f54c2a9
- Affected versionversion=7e76aece6f036cb7ada4858d6aa73825bfe22983 <3859960daeb9b7b39b9847b5b0113bc6081eb735
- Affected versionversion=7e76aece6f036cb7ada4858d6aa73825bfe22983 <6ad4f75ef9f3372fce8cad494e789ac6a5507bef
- Affected versionversion=7e76aece6f036cb7ada4858d6aa73825bfe22983 <8776032fe989a9b5fc77f2de5e03e4adb44c630e
- Affected versionversion=7e76aece6f036cb7ada4858d6aa73825bfe22983 <a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6
- Affected versionversion=7e76aece6f036cb7ada4858d6aa73825bfe22983 <ca5b0781946d5083ceafa752141f47f085853620
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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