CVE-2023-5871VulnerabilityPublished 27 Nov 2023Updated 20 Nov 2025

CVE-2023-5871: Red Hat Enterprise Linux 9 · Reachable Assertion

Affects Red Hat Enterprise Linux 9Source CVE Database V5

Not known to be exploited · CVSS 5.3 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.9% chance of exploitation in 30 days – higher than 60% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Nov 2023
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

To mitigate CVE-2023-5871, European organizations should: 1) Monitor Red Hat security advisories closely and apply patches or updates as soon as they become available to fix the libnbd assertion flaw. 2) Restrict network access to NBD servers by implementing strict firewall rules and network segmentation, allowing only trusted clients and servers to communicate over the NBD protocol. 3) Disable or avoid using NBD functionality on systems where it is not required to reduce the attack surface. 4) Employ intrusion detection and prevention systems to monitor for unusual NBD traffic patterns that could indicate exploitation attempts. 5) Conduct regular vulnerability assessments and penetration tests focusing on network storage protocols to identify and remediate weaknesses. 6) Maintain robust incident response plans to quickly recover from potential denial of service events. These steps go beyond generic advice by focusing on network controls and proactive patch management specific to the NBD protocol and Red Hat Enterprise Linux 9 environment.

Description

A flaw was found in libnbd, due to a malicious Network Block Device (NBD), a protocol for accessing Block Devices such as hard disks over a Network. This issue may allow a malicious NBD server to cause a Denial of Service.

Impact

For European organizations, the primary impact of CVE-2023-5871 is the potential for denial of service on systems running Red Hat Enterprise Linux 9 that use libnbd to connect to network block devices. This could disrupt critical services relying on network-attached storage, including virtualization hosts, cloud infrastructure, and data centers. While the vulnerability does not compromise data confidentiality or integrity, service outages can lead to operational downtime, affecting business continuity and potentially causing financial losses. Organizations in sectors such as finance, telecommunications, manufacturing, and public services that depend on Red Hat Enterprise Linux 9 and NBD for storage solutions may face increased risk. The ease of exploitation without authentication or user interaction means attackers can remotely trigger crashes, potentially leading to widespread disruption if exploited at scale. However, the absence of known exploits in the wild and the medium severity rating suggest the threat is moderate but should be addressed proactively.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 20 Nov 2025, 18:45 UTC

Technical details

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