CVE-2023-3036Network attack vector

Remote NTP service crash via unchecked extension read

Published Jun 14, 2023 · Updated Jan 2, 2025

Out-of-bounds read in Cloudflare cfnts before commit 783490b allows remote attackers to crash the NTP server with a malformed NTS packet. The parse_nts_packet function accepts a partial read of an attacker-declared extension, then computes a slice position as though every requested byte were present. No authentication or user interaction is required; one packet can panic the server and interrupt time service without exposing or modifying data.

CVSS severity8.6
High
EPSS probability2.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in Cloudflare cfnts before commit 783490b allows remote attackers to crash the NTP server with a malformed NTS packet. The parse_nts_packet function accepts a partial read of an attacker-declared extension, then computes a slice position as though every requested byte were present. No authentication or user interaction is required; one packet can panic the server and interrupt time service without exposing or modifying data.

The record

CVE
CVE-2023-3036
Published
Jun 14, 2023
Updated
Jan 2, 2025
Vendor
Cloudflare
Product
cfnts
Classifications
CWE-125, CWE-119, CAPEC-540, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 14, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 2, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 << 783490b

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloudflare · cfntsversion=0 << 783490b

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.6CloudflareCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
7.5GitHubCVSS:3.1/AV:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CAPEC-540Overread Buffers
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo