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Fencer Vulns
medium 5.3

CVE-2023-5215 json

Libnbd: crash or misbehaviour when nbd server returns an unexpected block size

published 2023-09-28 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-57545

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 57%
public exploits
0
none known

Summary

A flaw was found in libnbd. A server can reply with a block size larger than 2^63 (the NBD spec states the size is a 64-bit unsigned value). This issue could lead to an application crash or other unintended behavior for NBD clients that doesn't treat the return value of the nbd_get_size() function correctly.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 9 0:1.18.1-3.el9
  • libnbd Debian 14, Debian 13 1.16.5-1

debian advisories DEBIAN-CVE-2023-5215

  • libnbd RHEL 9 1.18.1-3.el9
  • nbdfuse RHEL 9 1.18.1-3.el9
  • ocaml-libnbd RHEL 9 1.18.1-3.el9
  • python3-libnbd RHEL 9 1.18.1-3.el9
  • libnbd-bash-completion RHEL 9 1.18.1-3.el9

red hat advisories RHSA-2024:2204

  • libnbd openSUSE Leap 15.5, openSUSE Leap 15.4 1.18.1-150300.8.15.1

suse advisories SUSE-SU-2023:4222-1

  • libnbd openSUSE Tumbleweed 1.18.0-1.1

opensuse advisories openSUSE-SU-2024:13278-1

  • libnbd AlmaLinux 9 1.18.1-3.el9
  • nbdfuse AlmaLinux 9 1.18.1-3.el9
  • ocaml-libnbd AlmaLinux 9 1.18.1-3.el9
  • python3-libnbd AlmaLinux 9 1.18.1-3.el9
  • libnbd-bash-completion AlmaLinux 9 1.18.1-3.el9

almalinux advisories ALSA-2024:2204

  • libnbd Alpine 3.24, Alpine 3.23, Alpine 3.22 +2 more 1.18.0-r0

alpine advisories ALPINE-CVE-2023-5215

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libnbd CBL-Mariner 2.0, Azure Linux 3.0 1.12.1-3

azure linux advisories AZL-31095AZL-34933

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-5215 updated cvss 5.3

libnbd: Crash or misbehaviour when NBD server returns an unexpected block size

  • Red Hat Enterprise Linux 8 libnbd, nbdfuse, ocaml-libnbd, python3-libnbd, libnbd-bash-completion Red Hat Enterprise Linux 8 Advanced Virtualization libnbd, nbdfuse, ocaml-libnbd, python3-libnbd, libnbd-bash-completion
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 9) libnbd 1.18.1-3.el9, nbdfuse 1.18.1-3.el9, python3-libnbd 1.18.1-3.el9, libnbd-bash-completion 1.18.1-3.el9 Red Hat Enterprise Linux CRB (v. 9) ocaml-libnbd 1.18.1-3.el9
    fixed: vendor fix RHSA-2024:2204

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.81% chance of exploitation in the next 30 days, higher than 57% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • listman.redhat.com https://listman.redhat.com/archives/libguestfs/2023-September/032635.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8 Advanced Virtualization

Classification

Weakness
  • CWE-241 Improper Handling of Unexpected Data Type
  • CWE-252 Unchecked Return Value

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.