dbcve.org
Debian LinuxOperating system · Debian

CVE-2015-7704

HIGH · 7.5 CVSS v3.1 Published 2017-08-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The ntpd client in NTP 4.x before 4.2.8p4 and 4.3.x before 4.3.77 allows remote attackers to cause a denial of service via a number of crafted "KOD" messages.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

The ntpd client in NTP versions 4.x before 4.2.8p4 and 4.3.x before 4.3.77 is vulnerable to remote denial of service via specially crafted Kiss-of-Death (KOD) messages. When an attacker sends multiple malicious KOD packets to a vulnerable NTP client, it can cause the service to become unresponsive or crash.

MitigationUpgrade NTP to version 4.2.8p4, 4.3.77, or later to patch this vulnerability. Alternatively, implement network-level filtering to restrict NTP traffic to trusted sources.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 7.0= 8.0= 9.0
Enterprise Linux DesktopOperating system
Affected:= 6.0= 7.0
Enterprise Linux ServerOperating system
Affected:= 6.0= 7.0
Enterprise Linux Server AusOperating system
Affected:= 6.5= 6.6= 7.3= 7.4= 7.6= 7.7
Enterprise Linux Server EusOperating system
Affected:= 6.5= 6.6= 6.7= 7.1= 7.3= 7.4= 7.5= 7.6= 7.7
Enterprise Linux Server TusOperating system
Affected:= 6.5= 6.6= 7.3= 7.6= 7.7
Enterprise Linux WorkstationOperating system
Affected:= 6.0= 7.0
XenserverApplication
Affected:= 6.0.2= 6.2.0= 6.5= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm NTP daemon is running
    Run 'systemctl status ntpd' on RHEL/CentOS, 'systemctl status ntp' on Debian, or 'ps aux | grep ntpd' to verify the ntpd process is active
    Affected if If ntpd is running, the system could be affected by this vulnerability
  2. Identify installed NTP version
    Run 'ntpd --version' or 'ntpq --version' to get the exact version number of the NTP installation
    Affected if Version is 4.x before 4.2.8p4 OR 4.3.x before 4.3.77 - compare your output to these thresholds
  3. Verify NTP is listening on network
    Run 'netstat -anup | grep :123' or 'ss -anup | grep :123' to confirm ntpd is bound to UDP port 123
    Affected if If ntpd is bound to accessible network interfaces, it can receive malicious KOD packets from attackers
  4. Check KOD processing configuration
    Examine /etc/ntp.conf for 'kod' or 'limited' directives in the restrict lines, or run 'ntpq -c rl' to query rate limiting settings
    Affected if If KOD processing is enabled and ntpd is network-accessible, the vulnerability can be triggered
  5. Confirm NTP is exposed to untrusted networks
    Review firewall rules with 'iptables -L -n' or 'firewall-cmd --list-all' to determine if UDP port 123 is open to untrusted sources
    Affected if If UDP port 123 is accessible from outside trusted networks, remote attackers can send malicious KOD packets

A system is affected if it runs a vulnerable NTP version (before 4.2.8p4 or 4.3.77) with ntpd listening on accessible network interfaces and KOD processing enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade NTP to version 4.2.8p4, 4.3.77, or later to patch this vulnerability. Alternatively, implement network-level filtering to restrict NTP traffic to trusted sources.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2015-7704 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2015-7704 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data