CVE-2026-63995

Kernel memory corruption via unchecked CMIS length

Published Jul 19, 2026 · Updated Jul 19, 2026

Out-of-bounds write in Linux Kernel allows local users to corrupt kernel memory through a malicious CMIS module firmware reply. The CMIS firmware update path passes the module-controlled start_cmd_payload_size directly to memcpy in cmis_fw_update_start_download(), although the destination holds only 112 bytes. Reachability requires a compatible transceiver, a crafted or corrupted CDB reply, and CAP_NET_ADMIN to start module flashing; corruption can crash the kernel or alter kernel memory.

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 write in Linux Kernel allows local users to corrupt kernel memory through a malicious CMIS module firmware reply. The CMIS firmware update path passes the module-controlled start_cmd_payload_size directly to memcpy in cmis_fw_update_start_download(), although the destination holds only 112 bytes. Reachability requires a compatible transceiver, a crafted or corrupted CDB reply, and CAP_NET_ADMIN to start module flashing; corruption can crash the kernel or alter kernel memory.

The record

CVE
CVE-2026-63995
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-787, T1068
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=c4f78134d45c9619339c96b4bea380b1d0699788 <0696709e951be54c699664adf546d16e28974d53
  3. Affected versionversion=c4f78134d45c9619339c96b4bea380b1d0699788 <12c2496a71f82f63617971ca9b730dffa05cf58b
  4. Affected versionversion=c4f78134d45c9619339c96b4bea380b1d0699788 <63112b4515469d00008452d9cfe3fb3bf1aa2df3
  5. Affected versionversion=c4f78134d45c9619339c96b4bea380b1d0699788 <a46340da00385be7fb16c62425ebc20006f2d5d8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.11; version=c4f78134d45c9619339c96b4bea380b1d0699788 <0696709e951be54c699664adf546d16e28974d53; version=c4f78134d45c9619339c96b4bea380b1d0699788 <12c2496a71f82f63617971ca9b730dffa05cf58b; version=c4f78134d45c9619339c96b4bea380b1d0699788 <63112b4515469d00008452d9cfe3fb3bf1aa2df3; version=c4f78134d45c9619339c96b4bea380b1d0699788 <a46340da00385be7fb16c62425ebc20006f2d5d8

Published CVSS scores

5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8kernel.orgCVSS:3.1/AV:L/AC:L/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
T1068Exploitation for Privilege Escalation

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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