VulnerabilityPublished 19 Jul 2026Updated 3 Aug 2026

CVE-2026-63923: Linux kernel · octeontx2-af: validate body pcifunc in rvu_mbox_handler_rep_event_notify

Source GCVE Database

Authoritative record:CVE-2026-63923· High 8.8

Not known to be exploited · CVSS 8.8 High · fixed in 4467fa514482bbce82f73788943c815f3d126ab3 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

8.8High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4467fa514482bbce82f73788943c815f3d126ab3, 2156a29aecfffa2eb7c558255690084efbe9f3b0, 68be0260e2a02ff9b18a8678d5f8d1715fa20138

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-95j3-7q26-w637

What to do

Upgrade Linux kernel to 4467fa514482bbce82f73788943c815f3d126ab3, 2156a29aecfffa2eb7c558255690084efbe9f3b0 or 68be0260e2a02ff9b18a8678d5f8d1715fa20138.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ b8fea84a0468404fe3b3327ad54d583950be9dec, < 4467fa514482bbce82f73788943c815f3d126ab3	Fixed in 4467fa514482bbce82f73788943c815f3d126ab3
LinuxLinux	Affected ≥ b8fea84a0468404fe3b3327ad54d583950be9dec, < 2156a29aecfffa2eb7c558255690084efbe9f3b0	Fixed in 2156a29aecfffa2eb7c558255690084efbe9f3b0
LinuxLinux	Affected ≥ b8fea84a0468404fe3b3327ad54d583950be9dec, < 68be0260e2a02ff9b18a8678d5f8d1715fa20138	Fixed in 68be0260e2a02ff9b18a8678d5f8d1715fa20138
LinuxLinux	Affected =6.13	Fixed in–

AI-suggested

The vulnerability has been resolved by adding validation of the pcifunc field using is_pf_func_valid() to reject malformed requests early. If you cannot patch yet, restrict access to VFs in switchdev representor mode and monitor for unusual mailbox message activity. Follow vendor advisories for updates and apply official fixes when available.

Description

A vulnerability in the Linux kernel's octeontx2-af driver allowed an attacker-controlled field (pcifunc) in a REP_EVENT_NOTIFY request to bypass bounds checks, leading to out-of-bounds memory writes. This occurs because the body pcifunc field was not validated before being used as an index into internal arrays, causing a slab-out-of-bounds write. The issue affects the handling of mailbox messages from virtual functions (VFs) attached to physical functions (PFs) in switchdev representor mode. The vulnerability has been resolved by adding proper validation of the pcifunc field using the existing is_pf_func_valid() check.

Impact

This vulnerability allows a local attacker with access to a VF attached to a PF in switchdev representor mode to cause out-of-bounds memory writes in kernel space. The CVSS score of 8.8 indicates high severity with potential for complete confidentiality, integrity, and availability compromise (C:H/I:H/A:H). The out-of-bounds write could lead to kernel memory corruption, potentially resulting in privilege escalation, denial of service, or arbitrary code execution within the kernel context.

Summary

The Linux kernel vulnerability CVE-2026-63923 involves the octeontx2-af driver's rvu_mbox_handler_rep_event_notify() function, which queues a sender-controlled REP_EVENT_NOTIFY request body without validating the nested pcifunc field. This attacker-controlled pcifunc is then used without bounds checking in functions rvu_get_pfvf(), rvu_get_pf(), and for mailbox device indexing, leading to out-of-bounds memory access. Specifically, an out-of-range pcifunc can cause an out-of-bounds write via ether_addr_copy() in the queued worker, as detected by KASAN. The vulnerability arises because the VF mailbox handler forwards all message IDs including REP_EVENT_NOTIFY without an allowlist, and the AF dispatcher only rewrites the header pcifunc, leaving the body pcifunc attacker-controlled. The fix involves rejecting malformed requests early by gating on the canonical is_pf_func_valid() function to ensure pcifunc is within valid range.

References

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