Skip to content
Noroxi
CVE-2023-5871· NVD / CVE Program· CNA redhat

Libnbd: malicious nbd server may crash libnbd

Noroxi assessment

Priority: Monitor (action score 21/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.92% (FIRST EPSS); higher than 59.5% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: libnbd (AlmaLinux:9) 1.18.1-3.el9; libnbd-bash-completion (AlmaLinux:9) 1.18.1-3.el9; libnbd-devel (AlmaLinux:9) 1.18.1-3.el9.

Low priority for now. Upgrade to libnbd (AlmaLinux:9) 1.18.1-3.el9; libnbd-bash-completion (AlmaLinux:9) 1.18.1-3.el9; libnbd-devel (AlmaLinux:9) 1.18.1-3.el9 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A flaw was found in libnbd, due to a malicious Network Block Device (NBD), a protocol for accessing Block Devices such as hard disks over a Network. This issue may allow a malicious NBD server to cause a Denial of Service.

MediumCVSS 5.3 · v3.1—No exploit Fix available
Published
Nov 27, 2023
Updated
Jun 17, 2026
EPSS
0.9% · 59th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

CNA vs NVD score

NVD
5.3
CNA · redhat
5.3
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2023-5871

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for redhat records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
redhatlibnbd
redhatenterprise linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • redhat enterprise linux9.0
  • redhat libnbd1.17.4 and later · before 1.18.2
  • redhat libnbd1.19.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • Red Hat Red Hat Enterprise Linux 6

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 7

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 8

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 9

    • 0:1.18.1-3.el9 and laternot affected · rpm

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:9libnbdbefore 1.18.1-3.el91.18.1-3.el9
AlmaLinux:9libnbd-bash-completionbefore 1.18.1-3.el91.18.1-3.el9
AlmaLinux:9libnbd-develbefore 1.18.1-3.el91.18.1-3.el9
AlmaLinux:9nbdfusebefore 1.18.1-3.el91.18.1-3.el9
AlmaLinux:9ocaml-libnbdbefore 1.18.1-3.el91.18.1-3.el9
AlmaLinux:9ocaml-libnbd-develbefore 1.18.1-3.el91.18.1-3.el9
AlmaLinux:9python3-libnbdbefore 1.18.1-3.el91.18.1-3.el9
Debian:13libnbdbefore 1.18.1-11.18.1-1
openSUSE:Leap 15.4libnbdbefore 1.18.1-150300.8.18.11.18.1-150300.8.18.1
openSUSE:Tumbleweedlibnbdbefore 1.18.1-2.11.18.1-2.1
Red Hat:enterprise_linux:9::appstreamlibnbdbefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreamlibnbd-bash-completionbefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreamlibnbd-debuginfobefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreamlibnbd-debugsourcebefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreamnbdfusebefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreamnbdfuse-debuginfobefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreamocaml-libnbd-debuginfobefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreampython3-libnbdbefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::appstreampython3-libnbd-debuginfobefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::crblibnbd-develbefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::crbocaml-libnbdbefore 0:1.18.1-3.el90:1.18.1-3.el9
Red Hat:enterprise_linux:9::crbocaml-libnbd-develbefore 0:1.18.1-3.el90:1.18.1-3.el9

Same product

redhat: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-14842Structured reply is a feature of the newstyle NBD protocol allowing the server to send a reply in chunks.
    40Plan
  • CVE-2023-5215Libnbd: crash or misbehaviour when nbd server returns an unexpected block size
    26Monitor
  • CVE-2022-0485A flaw was found in the copying tool `nbdcopy` of libnbd.
    19Monitor
  • CVE-2021-20286A flaw was found in libnbd 1.7.3.
    10Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:libnbd1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
almalinux:libnbd-bash-completion1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
almalinux:libnbd-devel1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
almalinux:nbdfuse1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
almalinux:ocaml-libnbd1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
almalinux:ocaml-libnbd-devel1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
almalinux:python3-libnbd1.18.1-3.el9 · AlmaLinux:9Package registry (OSV)
debian:libnbd1.18.1-1 · Debian:13Package registry (OSV)
opensuse:libnbd1.18.1-150300.8.18.1 · openSUSE:Leap 15.4Package registry (OSV)
red hat:libnbd0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libnbd-bash-completion0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libnbd-debuginfo0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libnbd-debugsource0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libnbd-devel0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::crbPackage registry (OSV)
red hat:nbdfuse0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nbdfuse-debuginfo0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:ocaml-libnbd0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::crbPackage registry (OSV)
red hat:ocaml-libnbd-debuginfo0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:ocaml-libnbd-devel0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::crbPackage registry (OSV)
red hat:python3-libnbd0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:python3-libnbd-debuginfo0:1.18.1-3.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
low · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
Low

Weakness class (CWE)

CWE-617 · Reachable Assertion

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records