CVE-2023-34328VulnerabilityPublished 5 Jan 2024Updated 3 Jun 2025

CVE-2023-34328: Xen · Vulnerability

Affects XenSource CVE Database V5

Mentioned vulnerabilities

Not known to be exploited · CVSS 5.5 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

5.5Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
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: 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: 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 5 Jan 2024
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

Specific mitigation steps include: 1) Applying any available Xen hypervisor patches or updates that address this vulnerability as soon as they are released by the Xen Project or vendor distributions. 2) Restricting access to Xen management interfaces and guest environments to trusted users only, minimizing the risk of local privilege exploitation. 3) Monitoring and auditing guest VM behavior for unusual breakpoint or debug register activity that could indicate attempts to exploit this vulnerability. 4) Considering disabling or limiting the use of paravirtualized guests on AMD CPUs if feasible, or isolating PV guests in less critical environments until patches are applied. 5) Employing host-level security controls such as SELinux or AppArmor to restrict hypervisor and guest interactions. 6) Engaging with cloud service providers to confirm their Xen hypervisor versions and patch status if using hosted services. 7) Maintaining up-to-date incident response plans to quickly address potential DoS incidents stemming from this vulnerability.

Description

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] AMD CPUs since ~2014 have extensions to normal x86 debugging functionality. Xen supports guests using these extensions. Unfortunately there are errors in Xen's handling of the guest state, leading to denials of service.1) CVE-2023-34327 - An HVM vCPU can end up operating in the context of a previous vCPUs debug mask state.2) CVE-2023-34328 - A PV vCPU can place a breakpoint over the live GDT. This allows the PV vCPU to exploit XSA-156 / CVE-2015-8104 and lock up the CPU entirely.

Impact

For European organizations, the primary impact of CVE-2023-34328 is a denial of service condition that could disrupt critical virtualized workloads hosted on Xen hypervisor environments using AMD processors. This can lead to service outages, reduced availability of cloud services, and potential operational downtime. Sectors relying heavily on virtualization such as financial services, telecommunications, government agencies, and cloud service providers could experience interruptions affecting business continuity and service level agreements. Although the vulnerability does not compromise confidentiality or integrity, the availability impact can be significant in environments where high uptime is mandatory. Additionally, the requirement for local or low-privilege access means that attackers or malicious insiders with limited access could trigger the DoS, raising concerns about insider threats or compromised tenants in multi-tenant cloud setups. The absence of known exploits reduces immediate risk but does not eliminate the need for vigilance, especially given the strategic importance of virtualization in European IT infrastructure.

Summary

CVE-2023-34328 is a medium-severity vulnerability affecting the Xen hypervisor, specifically related to its handling of paravirtualized (PV) virtual CPUs (vCPUs) on AMD processors with extended debugging functionality introduced since approximately 2014. Xen supports guests leveraging these AMD CPU debugging extensions, but errors in managing guest state have been identified. This vulnerability allows a PV vCPU to place a breakpoint over the live Global Descriptor Table (GDT), which can be exploited in conjunction with a previously known vulnerability (XSA-156 / CVE-2015-8104) to cause a complete CPU lockup, resulting in a denial of service (DoS). The issue arises because the PV vCPU can manipulate debug registers improperly, leading to system instability. The related CVE-2023-34327 affects hardware virtual machine (HVM) vCPUs but is distinct from CVE-2023-34328. The CVSS v3.1 base score for CVE-2023-34328 is 5.5, reflecting a medium severity with local attack vector, low complexity, requiring low privileges, no user interaction, and impacting availability only. No known exploits are currently reported in the wild, and no patches or affected version details are explicitly provided in the source data. This vulnerability primarily impacts environments running Xen hypervisor on AMD CPUs that utilize PV guests, potentially affecting cloud and virtualization infrastructures relying on Xen for workload isolation and management.

References

xenbits.xenproject.org/xsa/advisory-444.html (opens in a new tab)

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 4 Jul 2025, 04:42 UTC

Technical details

References

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