CVE-2023-32251VulnerabilityPublished 31 Jul 2025Updated 21 Nov 2025

CVE-2023-32251: Improper Restriction of Excessive Authentication Attempts

Source CVE Database V5

Not known to be exploited · CVSS 3.7 Low.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

3.7Low

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 40% 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:U/C:L/I:N/A:N

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

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: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
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: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 31 Jul 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 2026-10-26.

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 official Linux kernel repositories and vendor advisories closely for patches addressing CVE-2023-32251 and apply updates promptly once available. 2. Temporarily restrict or disable SMB/CIFS services on Linux systems running affected kernel versions if feasible, especially on systems exposed to untrusted networks. 3. Implement network-level controls such as firewall rules to limit SMB traffic to trusted hosts and internal networks only. 4. Enforce strong password policies and account lockout thresholds to reduce the effectiveness of brute-force attacks, compensating for the weakened delay mechanism. 5. Deploy intrusion detection or prevention systems capable of identifying abnormal authentication attempts or rapid session setups indicative of brute-force activity. 6. Consider additional authentication mechanisms such as multi-factor authentication (MFA) for SMB access where supported. 7. Conduct regular audits of SMB server logs to detect and respond to suspicious authentication patterns. 8. Educate system administrators about the vulnerability and the importance of timely patching and monitoring. These steps go beyond generic advice by focusing on compensating controls and proactive monitoring in the absence of immediate patches.

Description

A vulnerability has been identified in the Linux kernel's ksmbd component (kernel SMB/CIFS server). A security control designed to prevent dictionary attacks, which introduces a 5-second delay during session setup, can be bypassed through the use of asynchronous requests. This bypass negates the intended anti-brute-force protection, potentially allowing attackers to conduct dictionary attacks more efficiently against user credentials or other authentication mechanisms.

Impact

For European organizations, the primary impact of CVE-2023-32251 lies in the increased risk of successful brute-force or dictionary attacks against SMB authentication credentials. This could lead to unauthorized access to file shares and sensitive data hosted on SMB servers running on vulnerable Linux kernels. While the vulnerability itself does not directly compromise system integrity or availability, successful credential compromise can facilitate lateral movement, data exfiltration, or further exploitation within the network. Organizations in sectors with high reliance on SMB for file sharing, such as finance, manufacturing, and public administration, may face elevated risks. Additionally, critical infrastructure operators using Linux-based SMB servers could see increased threat activity targeting authentication mechanisms. The low CVSS score suggests limited immediate risk, but the bypass of a key security control means that existing defenses against brute-force attacks are weakened, potentially increasing the attack surface. The absence of known exploits reduces immediate urgency but does not eliminate future risk. European organizations should consider this vulnerability in their risk assessments, especially those with exposed SMB services or weak password policies.

References

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