CyberSecBulletin
CVE-2026-63949NVD status: Analyzed

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-63949 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions ca5b0781946d5083ceafa752141f47f085853620, 8776032fe989a9b5fc77f2de5e03e4adb44c630e, 3859960daeb9b7b39b9847b5b0113bc6081eb735 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to ca5b0781946d5083ceafa752141f47f085853620 or 8776032fe989a9b5fc77f2de5e03e4adb44c630e or 3859960daeb9b7b39b9847b5b0113bc6081eb735 or 197476b126010bac1b3199833c6966cd6f54c2a9, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.176 or 6.6.143 or 6.12.93 or 6.18.35, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux7e76aece6f036cb7ada4858d6aa73825bfe22983 up to, but not including, ca5b0781946d5083ceafa752141f47f085853620; 7e76aece6f036cb7ada4858d6aa73825bfe22983 up to, but not including, 8776032fe989a9b5fc77f2de5e03e4adb44c630e; 7e76aece6f036cb7ada4858d6aa73825bfe22983 up to, but not including, 3859960daeb9b7b39b9847b5b0113bc6081eb735; 7e76aece6f036cb7ada4858d6aa73825bfe22983 up to, but not including, 197476b126010bac1b3199833c6966cd6f54c2a9; 7e76aece6f036cb7ada4858d6aa73825bfe22983 up to, but not including, 6ad4f75ef9f3372fce8cad494e789ac6a5507bef; 7e76aece6f036cb7ada4858d6aa73825bfe22983 up to, but not including, a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6; 5.16ca5b0781946d5083ceafa752141f47f085853620, 8776032fe989a9b5fc77f2de5e03e4adb44c630e, 3859960daeb9b7b39b9847b5b0113bc6081eb735, 197476b126010bac1b3199833c6966cd6f54c2a9, 6ad4f75ef9f3372fce8cad494e789ac6a5507bef, a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6
LinuxLinux Kernel5.16 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.16.1.176, 6.6.143, 6.12.93, 6.18.35, 7.0.12

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: auxdisplay: line-display: fix OOB read on zero-length message_store() linedisp_display() 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); -> message_store(..., buf, count=0) -> linedisp_display(linedisp, buf, count=0) -> msg[count - 1] == '\n' ; OOB read The kernfs write buffer for that store is a 1-byte allocation (kernfs_fop_write_iter() 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 ssize_t 0 to -1 and is then passed to kmemdup_nul(). linedisp_display() is reached from the message_store() 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; vfs_write() does not short-circuit on count == 0 and kernfs_fop_write_iter() 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 linedisp_register() / linedisp_attach(): ht16k33, max6959, img-ascii-lcd, seg-led-gpio.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that provides appropriate memory abstractions.

More Out-of-bounds Read vulnerabilities (CWE-125)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Read vulnerabilities

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