CVE-2026-63996

Kernel memory corruption via oversized CDB reply

Published Jul 19, 2026 · Updated Jul 19, 2026

Out-of-bounds writes in Linux Kernel 6.11 allow local users to corrupt kernel memory through malicious CMIS module replies. cmis_cdb_process_reply() accepts rpl_len values larger than rpl_exp_len and copies the oversized payload into page_data, whose allocation is sized only to the expected reply. Triggering requires CAP_NET_ADMIN to start the module firmware-flash path and a malicious or faulty optical module; no crash or code execution has been demonstrated.

CVSS severity7.8
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds writes in Linux Kernel 6.11 allow local users to corrupt kernel memory through malicious CMIS module replies. cmis_cdb_process_reply() accepts rpl_len values larger than rpl_exp_len and copies the oversized payload into page_data, whose allocation is sized only to the expected reply. Triggering requires CAP_NET_ADMIN to start the module firmware-flash path and a malicious or faulty optical module; no crash or code execution has been demonstrated.

The record

CVE
CVE-2026-63996
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-787, T1200
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.11
  2. Affected versionversion=a39c84d796254e6b1662ca0c46dbc313379e9291 <2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3
  3. Affected versionversion=a39c84d796254e6b1662ca0c46dbc313379e9291 <4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1
  4. Affected versionversion=a39c84d796254e6b1662ca0c46dbc313379e9291 <6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1
  5. Affected versionversion=a39c84d796254e6b1662ca0c46dbc313379e9291 <eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.11; version=a39c84d796254e6b1662ca0c46dbc313379e9291 <2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3; version=a39c84d796254e6b1662ca0c46dbc313379e9291 <4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1; version=a39c84d796254e6b1662ca0c46dbc313379e9291 <6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1; version=a39c84d796254e6b1662ca0c46dbc313379e9291 <eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0Red HatCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1200Hardware Additions

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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