CVE-2023-34966VulnerabilityPublished 20 Jul 2023Updated 20 Nov 2025

CVE-2023-34966: Red Hat Enterprise Linux 8 · Infinite Loop

Affects Red Hat Enterprise Linux 8Source CVE Database V5

Not known to be exploited · 62% EPSS · CVSS 7.5 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 62.4% chance of exploitation in 30 days – higher than 99% 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:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
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: 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: 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 20 Jul 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

1. Apply official patches and updates from Red Hat as soon as they become available to address CVE-2023-34966. 2. Until patches are deployed, restrict network access to the Samba mdssvc RPC service by implementing firewall rules or network segmentation to limit exposure to trusted hosts only. 3. Monitor network traffic for unusual or malformed RPC requests targeting the mdssvc service, using intrusion detection/prevention systems (IDS/IPS) with updated signatures. 4. Employ resource usage monitoring on critical servers to detect abnormal CPU spikes that may indicate exploitation attempts. 5. Consider disabling the Spotlight mdssvc RPC service if it is not required in the environment to eliminate the attack vector. 6. Maintain an incident response plan to quickly respond to potential DoS incidents caused by this vulnerability. 7. Engage with Red Hat support and subscribe to security advisories to stay informed about patches and mitigation guidance.

Description

CVE-2023-34966 is a high-severity vulnerability in Red Hat Enterprise Linux 8's Samba mdssvc RPC service used for Spotlight. The flaw arises from improper validation of a count field in network packets, allowing an attacker to trigger an infinite loop by sending a malformed RPC request with a zero count value. This infinite loop causes 100% CPU consumption, leading to a denial of service (DoS) condition. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network. Although no known exploits are currently reported in the wild, the impact on availability is significant. European organizations relying on Red Hat Enterprise Linux 8 servers running Samba services are at risk, especially those in critical infrastructure and enterprise environments. Mitigation involves applying vendor patches once available and implementing network-level filtering to restrict access to the vulnerable RPC service. Countries with high adoption of Red Hat Enterprise Linux, such as Germany, France, and the UK, are most likely to be affected.

Impact

For European organizations, the primary impact is a denial of service condition that can disrupt critical services relying on Red Hat Enterprise Linux 8 servers running Samba's mdssvc RPC service. This can lead to downtime, loss of productivity, and potential cascading effects on dependent applications and services. Organizations in sectors such as finance, telecommunications, government, and critical infrastructure that use Red Hat Enterprise Linux 8 are particularly vulnerable. The infinite loop causing 100% CPU utilization can degrade system performance severely, potentially requiring system reboots or manual intervention to restore service. Since the vulnerability is remotely exploitable without authentication, attackers can launch DoS attacks from external networks, increasing the threat surface. Although no data confidentiality or integrity loss is expected, the availability impact alone can cause significant operational and reputational damage. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for future attacks.

Summary

CVE-2023-34966 is a vulnerability identified in the Samba mdssvc RPC service component of Red Hat Enterprise Linux 8, specifically related to the Spotlight feature. The core issue lies in the unmarshalling function sl_unpack_loop(), which processes RPC packets containing an array-like structure with a count field indicating the number of elements. The function fails to validate this count field properly. An attacker can exploit this by sending a malformed RPC request with the count set to zero, causing the function to enter an infinite loop. This loop consumes 100% CPU resources on the affected system, effectively causing a denial of service (DoS) by exhausting processing capacity. The vulnerability is remotely exploitable without any authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score is 7.5 (high), reflecting the network attack vector, low attack complexity, no privileges required, no user interaction, and a high impact on availability. While confidentiality and integrity are unaffected, the availability impact can disrupt critical services relying on Samba and Spotlight RPC services. No known public exploits have been reported yet, but the flaw's nature suggests it could be weaponized for DoS attacks. The vulnerability affects Red Hat Enterprise Linux 8 installations running the vulnerable Samba mdssvc RPC service, which is commonly used in enterprise and server environments.

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Description

AI analysisMachine-generated, updated 27 Nov 2025, 17:40 UTC

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