CVE-2023-32256VulnerabilityPublished 1 Aug 2025Updated 20 Nov 2025

CVE-2023-32256: Race Condition During Access to Alternate Channel

Source CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within 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 1 Aug 2025
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 2026-10-25.

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 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.

What to do

AI-suggested

1. Monitor vendor and Linux kernel mailing lists for official patches addressing CVE-2023-32256 and apply them promptly once available. 2. Temporarily disable SMB multichannel support in the ksmbd configuration if multichannel is not essential for your environment, reducing attack surface. 3. Implement strict network segmentation and firewall rules to limit SMB traffic exposure to trusted networks and hosts only. 4. Enhance monitoring of system logs and kernel messages for signs of ksmbd crashes, use-after-free errors, or unusual SMB session terminations. 5. Conduct regular kernel and system integrity checks to detect anomalies potentially caused by exploitation attempts. 6. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and memory protection features to mitigate exploitation impact. 7. Educate system administrators about the vulnerability and encourage rapid response to any ksmbd-related service disruptions. 8. Review and restrict SMB server usage to only necessary systems and services to minimize the number of exposed targets. 9. Prepare incident response plans specifically addressing potential denial of service scenarios related to SMB services. 10. Consider deploying intrusion detection systems capable of identifying abnormal SMB traffic patterns indicative of exploitation attempts.

Description

A flaw was found in the Linux kernel's ksmbd component. A race condition between smb2 close operation and logoff in multichannel connections could result in a use-after-free issue.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of Linux-based SMB file sharing services, which are commonly used in enterprise environments for internal file access and collaboration. Disruption of SMB services due to denial of service can impact business operations, especially in sectors relying on continuous access to shared resources such as finance, manufacturing, healthcare, and public administration. The use-after-free condition could lead to system crashes or kernel panics, causing downtime and potential data access interruptions. Although confidentiality and integrity impacts are limited, the availability impact alone can result in operational delays and increased incident response costs. Organizations using multichannel SMB connections to enhance performance or redundancy are particularly vulnerable. Given the network attack vector and lack of required privileges, remote attackers could exploit this flaw without authentication, increasing the threat surface. The absence of known exploits in the wild reduces immediate risk but does not eliminate the potential for future attacks, especially as exploit techniques evolve. European entities with critical infrastructure or large-scale Linux deployments should prioritize mitigation to prevent service outages and maintain compliance with operational resilience requirements. Additionally, the vulnerability could be leveraged as part of a broader attack chain to disrupt services or distract from other malicious activities.

References

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