CVE-2023-46838VulnerabilityPublished 29 Jan 2024Updated 2 Jun 2025

CVE-2023-46838: Linux · Vulnerability

Affects LinuxSource 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: 1.1% chance of exploitation in 30 days – higher than 67% 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 29 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 2026-10-25.

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

European organizations should prioritize the following mitigation steps: 1) Identify all Linux systems running Xen virtualization and assess their exposure to network traffic that could exploit this vulnerability. 2) Monitor vendor and Linux kernel mailing lists for patches or updates addressing CVE-2023-46838 and apply them promptly once available. 3) Implement network-level protections such as filtering or rate-limiting suspicious or malformed Xen virtual network protocol packets to reduce attack surface. 4) Employ intrusion detection systems (IDS) or anomaly detection tools tuned to detect unusual Xen network traffic patterns indicative of exploitation attempts. 5) For critical systems, consider temporary isolation or migration to alternative virtualization platforms until patches are applied. 6) Conduct thorough testing of updates in staging environments to ensure stability and compatibility. 7) Maintain robust incident response plans to quickly recover from potential denial-of-service incidents caused by this vulnerability. These measures go beyond generic advice by focusing on the specific Xen virtualization context and the nature of the zero-length SKB fragment exploitation vector.

Description

Transmit requests in Xen's virtual network protocol can consist of multiple parts. While not really useful, except for the initial part any of them may be of zero length, i.e.carry no data at all. Besides a certain initial portion of the to be transferred data, these parts are directly translated into what Linux calls SKB fragments. Such converted request parts can, when for a particular SKB they are all of length zero, lead to a de-reference of NULL in core networking code.

Impact

For European organizations, especially those relying on Linux servers in Xen virtualized environments, this vulnerability poses a significant risk of service disruption. The ability to remotely cause a kernel panic without authentication means attackers can launch denial-of-service attacks against critical infrastructure, cloud services, or enterprise applications hosted on vulnerable systems. This could affect cloud service providers, hosting companies, financial institutions, telecommunications, and government agencies that use Xen-based virtualization. The disruption of availability could lead to operational downtime, loss of productivity, and potential cascading effects on dependent services. Although there is no direct impact on confidentiality or integrity, the availability impact alone can be severe, particularly for organizations with strict uptime requirements or those providing essential services. The lack of known exploits in the wild suggests limited immediate threat, but the ease of exploitation and high impact warrant urgent attention.

Summary

CVE-2023-46838 is a high-severity vulnerability affecting the Linux kernel's handling of transmit requests in Xen's virtual network protocol. Xen is a popular open-source hypervisor used to create and manage virtual machines. The vulnerability arises because transmit requests can be composed of multiple parts, and except for the initial part, any of these parts may be zero-length, meaning they carry no data. These parts are converted into socket buffer (SKB) fragments within the Linux networking stack. If all the SKB fragments for a particular socket buffer are zero-length, this leads to a NULL pointer dereference in the core networking code. This dereference can cause a kernel panic or system crash, resulting in a denial of service (DoS) condition. The CVSS 3.1 score is 7.5 (high), reflecting that the vulnerability can be exploited remotely over the network without authentication or user interaction, and it impacts availability but not confidentiality or integrity. There are no known exploits in the wild as of the publication date, and no patches are linked yet. The underlying weakness is classified as CWE-476 (NULL Pointer Dereference). This vulnerability specifically targets Linux systems running Xen virtualized environments, which are common in cloud and enterprise data centers. Exploiting this flaw requires sending crafted network packets that trigger the zero-length SKB fragment condition, causing the kernel to crash and disrupt services running on the affected host or virtual machine.

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 3 Jul 2025, 17:57 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

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