CyberSecBulletin
CVE-2026-63856NVD status: Modified

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/vcn: set…

Published Updated By the CyberSecBulletin desk

CVE-2026-63856 is a high-severity improper input validation 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 bcb972496f189edbf56a18b14f9b4831fd127ab8, f264019be80de79f84f464846451445923bffea0, 5e777bc4cbe928ac0fd95e368fee1540f2ce4db2 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 bcb972496f189edbf56a18b14f9b4831fd127ab8 or f264019be80de79f84f464846451445923bffea0 or 5e777bc4cbe928ac0fd95e368fee1540f2ce4db2 or ac06ce5cac9e711281585d09d00c6efcd9b86396, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.141 or 6.12.91 or 6.18.33 or 7.0.10, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux1b61de45dfaff00b627e47349a019658e39268b9 up to, but not including, bcb972496f189edbf56a18b14f9b4831fd127ab8; 1b61de45dfaff00b627e47349a019658e39268b9 up to, but not including, f264019be80de79f84f464846451445923bffea0; 1b61de45dfaff00b627e47349a019658e39268b9 up to, but not including, 5e777bc4cbe928ac0fd95e368fee1540f2ce4db2; 1b61de45dfaff00b627e47349a019658e39268b9 up to, but not including, ac06ce5cac9e711281585d09d00c6efcd9b86396; 1b61de45dfaff00b627e47349a019658e39268b9 up to, but not including, c71aecae98e42dcf2baf462df50b3a2cf1a93fe4; 1b61de45dfaff00b627e47349a019658e39268b9 up to, but not including, 8d80b293b41fcb5e9396db93e788b0f4ebcbafb7; 5.3bcb972496f189edbf56a18b14f9b4831fd127ab8, f264019be80de79f84f464846451445923bffea0, 5e777bc4cbe928ac0fd95e368fee1540f2ce4db2, ac06ce5cac9e711281585d09d00c6efcd9b86396, c71aecae98e42dcf2baf462df50b3a2cf1a93fe4, 8d80b293b41fcb5e9396db93e788b0f4ebcbafb7
LinuxLinux Kernel5.3 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.10; 7.16.6.141, 6.12.91, 6.18.33, 7.0.10

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 CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings VCN encoder and decoder rings do not support 64-bit user fence writes, reject CS submissions with user fences. (cherry picked from commit e2b5499fca55f1a32960a311bbb62e35891eaf73)

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

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Input Validation vulnerabilities

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