CVE-2023-5215Public exploit

Client crash via oversized NBD export size

Published Sep 28, 2023 · Updated Nov 8, 2025

Improper size handling in libnbd on Red Hat Enterprise Linux 8, Advanced Virtualization 8, and 9 allows remote attackers to crash NBD clients. The nbd_get_size API converts an unsigned server export size above INT64_MAX into a negative int64_t value other than the documented -1 error, which external callers can accept as success. Reachability requires a client connection to an attacker-controlled or modified noncompliant NBD server; libnbd's own client code is unaffected, but dependent applications can crash or misbehave.

CVSS severity5.3
Medium
EPSS probability0.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper size handling in libnbd on Red Hat Enterprise Linux 8, Advanced Virtualization 8, and 9 allows remote attackers to crash NBD clients. The nbd_get_size API converts an unsigned server export size above INT64_MAX into a negative int64_t value other than the documented -1 error, which external callers can accept as success. Reachability requires a client connection to an attacker-controlled or modified noncompliant NBD server; libnbd's own client code is unaffected, but dependent applications can crash or misbehave.

The record

CVE
CVE-2023-5215
Published
Sep 28, 2023
Updated
Nov 8, 2025
Vendor
Red Hat
Product
Red Hat Enterprise Linux 8
Classifications
CWE-241, CWE-252, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 28, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Red Hat · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8 Advanced VirtualizationAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.

Published CVSS scores

5.3Red Hat, Inc.CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
6.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-241Improper Handling of Unexpected Data Type
CWE-252Unchecked Return Value
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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