CyberSecBulletin
CVE-2026-63898NVD status: Analyzed

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-63898 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 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 94edbbc5fe00d03cfe1d4e690d7d2cd36317a935, bd2ddb3fe9052ad8703593bbec26ecc7ca92869e, 39e295a91e80f3b91f61c7ada2bde434dcaba20d 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 0.18% 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 94edbbc5fe00d03cfe1d4e690d7d2cd36317a935 or bd2ddb3fe9052ad8703593bbec26ecc7ca92869e or 39e295a91e80f3b91f61c7ada2bde434dcaba20d or 90dbad14b109e5fdfb4934ff61e561d11ba3742d, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.259 or 5.15.210 or 6.1.176 or 6.6.143, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 94edbbc5fe00d03cfe1d4e690d7d2cd36317a935; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, bd2ddb3fe9052ad8703593bbec26ecc7ca92869e; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 39e295a91e80f3b91f61c7ada2bde434dcaba20d; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 90dbad14b109e5fdfb4934ff61e561d11ba3742d; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 6cb48f8890f9b2051d7c34823057296a536a31c5; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, d8fdf33d6fcfb90cbec26299baf2352c84b2d768; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 57f332af1745014cd7e40414814ffaa6bc7d3b5b; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 915b36d701950503c4ea0f6e314b10868e59fce3; and 1 more ranges94edbbc5fe00d03cfe1d4e690d7d2cd36317a935, bd2ddb3fe9052ad8703593bbec26ecc7ca92869e, 39e295a91e80f3b91f61c7ada2bde434dcaba20d, 90dbad14b109e5fdfb4934ff61e561d11ba3742d, 6cb48f8890f9b2051d7c34823057296a536a31c5, d8fdf33d6fcfb90cbec26299baf2352c84b2d768
LinuxLinux Kernel2.6.12.1 up to, but not including, 5.10.259; 5.11 up to, but not including, 5.15.210; 5.16 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, 6.12.94; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 2.6.12; and 1 more ranges5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.35

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
HighData or code can be modified at will.
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:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: USB: serial: mct_u232: fix memory corruption with small endpoint The driver overrides the maximum transfer size for a specific device which only accepts 16 byte packets for its 32 byte bulk-out endpoint. Make sure to never increase the maximum transfer size to prevent slab corruption should a malicious device report a smaller endpoint max packet size than expected.

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

The underlying weakness: Out-of-bounds Write

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

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

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

References

Recent Out-of-bounds Write vulnerabilities

Spotted an error? Tell us.