CVE-2026-63923

Host kernel corruption via unchecked mailbox pcifunc

Published Jul 19, 2026 · Updated Jul 19, 2026

Out-of-bounds write in Linux Kernel 6.13 allows local users with an assigned OcteonTX2 VF to corrupt host kernel memory. The rvu_mbox_handler_rep_event_notify function queues a sender-controlled request, and rvu_rep_up_notify uses its unchecked pcifunc to index PF or VF arrays before ether_addr_copy writes six attacker-chosen bytes out of bounds. Reachability requires Marvell OcteonTX2 hardware, switchdev representor mode, and control of an assigned SR-IOV VF; network packets cannot reach the mailbox path.

CVSS severity8.8
High
EPSS probability0.17%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Linux Kernel 6.13 allows local users with an assigned OcteonTX2 VF to corrupt host kernel memory. The rvu_mbox_handler_rep_event_notify function queues a sender-controlled request, and rvu_rep_up_notify uses its unchecked pcifunc to index PF or VF arrays before ether_addr_copy writes six attacker-chosen bytes out of bounds. Reachability requires Marvell OcteonTX2 hardware, switchdev representor mode, and control of an assigned SR-IOV VF; network packets cannot reach the mailbox path.

The record

CVE
CVE-2026-63923
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
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=6.13
  2. Affected versionversion=b8fea84a0468404fe3b3327ad54d583950be9dec <2156a29aecfffa2eb7c558255690084efbe9f3b0
  3. Affected versionversion=b8fea84a0468404fe3b3327ad54d583950be9dec <68be0260e2a02ff9b18a8678d5f8d1715fa20138

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.13; version=b8fea84a0468404fe3b3327ad54d583950be9dec <2156a29aecfffa2eb7c558255690084efbe9f3b0; version=b8fea84a0468404fe3b3327ad54d583950be9dec <68be0260e2a02ff9b18a8678d5f8d1715fa20138

Published CVSS scores

8.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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