CVE-2026-63949: auxdisplay: line-display: fix OOB read on zero-length message_store()

Q: What access is required to trigger this issue?

An attacker needs local access and permission to write to the line-display message sysfs attribute. The affected callback is exposed through a sysfs attribute with mode 0644.

Q: What specific operation reaches the vulnerable path?

The userspace-triggerable path is a zero-byte write to the message sysfs attribute. The in-tree initial-message setup also reaches the display function, but the out-of-bounds path is described as userspace-triggerable only through zero-byte writes.

Q: What symptoms should defenders expect?

On kernels with KASAN enabled, the out-of-bounds read can produce a KASAN report and panic the kernel. On stock kernels, it may silently read adjacent slab data; if that byte is a newline, a subsequent length decrement can wrap zero to -1 before it is passed to kmemdup_nul().

Published Jul 19, 2026

Updated

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

auxdisplay: line-display: fix OOB read on zero-length messagestore()

linedispdisplay() unconditionally reads msg[count - 1] before checking whether count is zero, so a write of zero bytes to the message sysfs attribute hits msg[-1]:

write(fd, "", 0);

-> messagestore(..., buf, count=0) -> linedispdisplay(linedisp, buf, count=0) -> msg[count - 1] == '\n' ; OOB read

The kernfs write buffer for that store is a 1-byte allocation (kernfsfopwriteiter() does kmalloc(len + 1) with len == 0), so msg[-1] is a 1-byte read before the slab object. On a KASAN-enabled kernel this trips an out-of-bounds report and panics; on stock kernels it silently reads adjacent slab data and, if that byte happens to be '\n', the following count-- wraps ssizet 0 to -1 and is then passed to kmemdupnul().

linedispdisplay() is reached from the messagestore() sysfs callback (drivers/auxdisplay/line-display.c message attribute, mode 0644) and from the in-tree initial-message setup with count == -1, so the OOB path is only userspace-triggerable via zero-byte writes; vfswrite() does not short-circuit on count == 0 and kernfsfopwriteiter() dispatches the store callback regardless.

Guard the trailing-newline trim with a count check. The existing if (!count) block then takes the clear-display path unchanged.

Affects every auxdisplay driver that registers via linedispregister() / linedispattach(): ht16k33, max6959, img-ascii-lcd, seg-led-gpio.

Affected Software

181 affected componentsFixes available

Linux Linux kernel (auxdisplay line-display)

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.8*

ubuntu/linux-intel-5.13*

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.8*

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1066.69~22.04.1

6.8.0-1066.69~22.04.1

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1070.78~22.04.1

6.8.0-1070.78~22.04.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1068.75~22.04.1

6.8.0-1068.75~22.04.1

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1070.78~22.04.1

6.8.0-1070.78~22.04.1

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-ibm-6.8<6.8.0-1066.67~22.04.1

6.8.0-1066.67~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-146.146.1~22.04.1

6.8.0-146.146.1~22.04.1

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1064.67~22.04.1

6.8.0-1064.67~22.04.1

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-146.146~22.04.1

6.8.0-146.146~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-realtime-6.8<6.8.1-1061.62~22.04.1

6.8.1-1061.62~22.04.1

ubuntu/linux<6.8.0-146.146

6.8.0-146.146

ubuntu/linux-aws<6.8.0-1066.69

6.8.0-1066.69

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17*

ubuntu/linux-azure<6.8.0-1070.78

6.8.0-1070.78

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-6.17*

ubuntu/linux-azure-7.0<7.0.0-1014.14~24.04.1

7.0.0-1014.14~24.04.1

ubuntu/linux-azure-fde<6.8.0-1068.75

6.8.0-1068.75

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-fde-6.17*

ubuntu/linux-azure-fde-7.0<7.0.0-1013.13~24.04.1

7.0.0-1013.13~24.04.1

ubuntu/linux-azure-nvidia*

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1070.78

6.8.0-1070.78

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-7.0<7.0.0-1011.11~24.04.1

7.0.0-1011.11~24.04.1

ubuntu/linux-gke<6.8.0-1065.73

6.8.0-1065.73

ubuntu/linux-gkeop<6.8.0-1051.55

6.8.0-1051.55

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17*

ubuntu/linux-hwe-7.0<7.0.0-28.28~24.04.1

7.0.0-28.28~24.04.1

ubuntu/linux-ibm<6.8.0-1066.67

6.8.0-1066.67

ubuntu/linux-lowlatency<6.8.0-146.146.1

6.8.0-146.146.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1064.67

6.8.0-1064.67

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17*

ubuntu/linux-nvidia-7.0<7.0.0-1016.16~24.04.1

7.0.0-1016.16~24.04.1

ubuntu/linux-nvidia-lowlatency<6.8.0-1064.67.1

6.8.0-1064.67.1

ubuntu/linux-nvidia-tegra*

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17*

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1063.66

6.8.0-1063.66

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17*

ubuntu/linux-oracle-7.0<7.0.0-1011.11~24.04.1

7.0.0-1011.11~24.04.1

ubuntu/linux-raspi*

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-riscv-6.17*

ubuntu/linux-riscv-7.0<7.0.0-28.28.1~24.04.3

7.0.0-28.28.1~24.04.3

ubuntu/linux-xilinx*

ubuntu/linux-bluefield<6.8.0-1032.37

6.8.0-1032.37

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime<6.8.1-1061.62

6.8.1-1061.62

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17*

ubuntu/linux-aws-fips<6.8.0-1066.69+fips1

6.8.0-1066.69+fips1

ubuntu/linux-azure-fips<6.8.0-1069.77+fips1

6.8.0-1069.77+fips1

ubuntu/linux-fips<6.8.0-146.146+fips1

6.8.0-146.146+fips1

ubuntu/linux-gcp-fips<6.8.0-1070.78+fips1

6.8.0-1070.78+fips1

ubuntu/linux<7.0.0-28.28

7.0.0-28.28

ubuntu/linux-aws<7.0.0-1009.9

7.0.0-1009.9

ubuntu/linux-azure<7.0.0-1010.10

7.0.0-1010.10

ubuntu/linux-azure-fde<7.0.0-1009.9

7.0.0-1009.9

ubuntu/linux-gcp<7.0.0-1008.8

7.0.0-1008.8

ubuntu/linux-gke<7.0.0-1003.4

7.0.0-1003.4

ubuntu/linux-ibm<7.0.0-1010.10

7.0.0-1010.10

ubuntu/linux-nvidia<7.0.0-1016.16

7.0.0-1016.16

ubuntu/linux-nvidia-bos<7.0.0-2016.16

7.0.0-2016.16

ubuntu/linux-oem-7.0<7.0.0-1009.9

7.0.0-1009.9

ubuntu/linux-oracle<7.0.0-1008.8

7.0.0-1008.8

ubuntu/linux-raspi<7.0.0-1015.15

7.0.0-1015.15

ubuntu/linux-realtime<7.0.0-28.28.1

7.0.0-28.28.1

ubuntu/linux-riscv<7.0.0-28.28.1

7.0.0-28.28.1

Linux Linux kernel>=5.16<6.1.176

Linux Linux kernel>=6.2<6.6.143

Linux Linux kernel>=6.7<6.12.93

Linux Linux kernel>=6.13<6.18.35

Linux Linux kernel>=6.19<7.0.12

Linux Linux kernel=7.1-rc1

Linux Linux kernel=7.1-rc2

Linux Linux kernel=7.1-rc3

Linux Linux kernel=7.1-rc4

Linux Linux kernel=7.1-rc5

Linux Linux kernel=7.1-rc6

debian/linux<6.1.176-1

6.1.176-1

debian/linux<6.12.94-1

6.12.94-1

debian/linux<7.0.12-1

7.0.12-1

linux/kernel>=5.16.0<6.1.176

6.1.176

linux/kernel>=6.2.0<6.6.143

6.6.143

linux/kernel>=6.7.0<6.12.93

6.12.93

linux/kernel>=6.13.0<6.18.35

6.18.35

linux/kernel>=6.19.0<7.0.12

7.0.12

debian/linux

6.1.176-16.1.190-16.12.107-16.12.115-27.2.12-17.2.15-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1066.69~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1070.78~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1068.75~22.04.1
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Fixed in 6.8.0-1070.78~22.04.1
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Fixed in 6.8.0-1066.67~22.04.1
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Fixed in 6.8.0-146.146.1~22.04.1
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Fixed in 6.8.0-1064.67~22.04.1
Upgrade
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Fixed in 6.8.0-146.146~22.04.1
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1061.62~22.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-146.146
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1066.69
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1070.78
Upgrade
Upgrade ubuntu/linux-azure-7.0 to a version that resolves this vulnerability.
Fixed in 7.0.0-1014.14~24.04.1
Upgrade
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Fixed in 6.8.0-1068.75
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Fixed in 7.0.0-1013.13~24.04.1
Upgrade
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Fixed in 6.8.0-1070.78
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Fixed in 7.0.0-1011.11~24.04.1
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Fixed in 6.8.0-1065.73
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Fixed in 6.8.0-1051.55
Upgrade
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Fixed in 7.0.0-28.28~24.04.1
Upgrade
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Fixed in 6.8.0-1066.67
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-146.146.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1064.67
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Fixed in 7.0.0-1016.16~24.04.1
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Fixed in 6.8.0-1064.67.1
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Fixed in 6.8.0-1063.66
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Fixed in 7.0.0-1011.11~24.04.1
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Fixed in 7.0.0-28.28.1~24.04.3
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Fixed in 6.8.0-1032.37
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Fixed in 6.8.1-1061.62
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Fixed in 6.8.0-1066.69+fips1
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Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1069.77+fips1
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Fixed in 6.8.0-146.146+fips1
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Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1070.78+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 7.0.0-28.28
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Fixed in 7.0.0-1009.9
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Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 7.0.0-1010.10
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Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 7.0.0-1009.9
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Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 7.0.0-1008.8
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Fixed in 7.0.0-1003.4
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Fixed in 7.0.0-1010.10
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Fixed in 7.0.0-1016.16
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Fixed in 7.0.0-2016.16
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Fixed in 7.0.0-1009.9
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Fixed in 7.0.0-1008.8
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Fixed in 7.0.0-1015.15
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Fixed in 7.0.0-28.28.1
Upgrade
Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.
Fixed in 7.0.0-28.28.1
Upgrade
Upgrade debian/linux to a version that resolves this vulnerability.
Fixed in 6.1.176-1
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Fixed in 6.12.94-1
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Fixed in 7.0.12-1
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Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.14-1
Upgrade
Upgrade linux/Kernel to a version that resolves this vulnerability.
Fixed in 6.1.176
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Upgrade linux/Kernel to a version that resolves this vulnerability.
Fixed in 6.6.143
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Upgrade linux/Kernel to a version that resolves this vulnerability.
Fixed in 6.12.93
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Upgrade linux/Kernel to a version that resolves this vulnerability.
Fixed in 6.18.35
Upgrade
Upgrade linux/Kernel to a version that resolves this vulnerability.
Fixed in 7.0.12
Compensating control
In drivers/auxdisplay/line-display.c, guard the trailing-newline trim so msg[count - 1] is accessed only after checking that count is nonzero; this fixes zero-length message_store() writes for auxdisplay drivers registered via linedisp_register() or linedisp_attach().

Event History

Jul 19, 2026

CVE Published

via MITRE·02:55 PM

Data Sourced

via MITRE·02:55 PM

Description

Data Sourced

via OSV·02:55 PM

DescriptionAffected Software

Data Sourced

via NVD·04:17 PM

RemedyDescriptionSeverityWeaknessAffected Software

Data Sourced

via OSV·04:17 PM

Severity

Frequently Asked Questions

What access is required to trigger this issue?

An attacker needs local access and permission to write to the line-display message sysfs attribute. The affected callback is exposed through a sysfs attribute with mode 0644.

What specific operation reaches the vulnerable path?

The userspace-triggerable path is a zero-byte write to the message sysfs attribute. The in-tree initial-message setup also reaches the display function, but the out-of-bounds path is described as userspace-triggerable only through zero-byte writes.

What symptoms should defenders expect?

On kernels with KASAN enabled, the out-of-bounds read can produce a KASAN report and panic the kernel. On stock kernels, it may silently read adjacent slab data; if that byte is a newline, a subsequent length decrement can wrap zero to -1 before it is passed to kmemdup_nul().

CVE-2026-63949: auxdisplay: line-display: fix OOB read on zero-length message_store()

Affected Software

Remediation

Event History

Frequently Asked Questions

What access is required to trigger this issue?

What specific operation reaches the vulnerable path?

What symptoms should defenders expect?

Company

Resources

Contact

Frequently Asked Questions

What access is required to trigger this issue?

What specific operation reaches the vulnerable path?

What symptoms should defenders expect?