dbcve.org
FreeBSDOperating system

CVE-2015-7973

MEDIUM · 6.5 CVSS v3.1 Published 2017-01-30
Fix available
A fix is available. Upgrade to 4.2.8 / 4.3.90 or later.
See remediation →
74/100
Remediation priority · Elevated
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
NTP before 4.2.8p6 and 4.3.x before 4.3.90, when configured in broadcast mode, allows man-in-the-middle attackers to conduct replay attacks by sniffing the network.

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 · high confidence

NTP versions before 4.2.8p6 and 4.3.x before 4.3.90 contain a replay attack vulnerability when configured in broadcast mode. An attacker positioned on the network can capture (sniff) NTP broadcast packets and replay them to clients, causing them to accept duplicate or old time values. This can disrupt time synchronization and potentially affect systems relying on accurate time for authentication or cryptographic operations.

MitigationUpgrade NTP to version 4.2.8p6 or later (or 4.3.90+ for the 4.3.x branch). If upgrade is not feasible, disable NTP broadcast mode or implement authenticated broadcast mode to prevent unauthorized packet injection.

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
FreeBSDOperating system
Affected:>= 10.0, < 10.1= 9.3= 10.1= 10.2
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 16.04
NtpApplication
Affected:< 4.2.8>= 4.3.0, < 4.3.90= 4.2.8
Tim 4r Ie FirmwareOperating system
Affected:all versions
Tim 4r Ie Dnp3 FirmwareOperating system
Affected:all versions
Clustered Data OntapApplication
Affected:all versions
Oncommand BalanceApplication
Affected:all versions

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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. Identify NTP package version
    Run 'ntpd --version' or 'ntpq -c version' to get the NTP daemon version. On Ubuntu/Debian: 'dpkg -l | grep ntp'. On FreeBSD: 'pkg info ntp'.
    Affected if Version is earlier than 4.2.8p6 OR falls between 4.3.0 and 4.3.90 (exclusive of 4.3.90).
  2. Confirm NTP broadcast client mode is active
    Inspect the NTP configuration file (typically /etc/ntp.conf) for the 'broadcastclient' directive, or run 'ntpq -c peers' to see if the local system is listening for broadcast packets.
    Affected if The 'broadcastclient' directive is present in ntp.conf, indicating the system listens to NTP broadcasts.
  3. Verify broadcast mode is actually in use
    Check 'ntpq -c associations' output. Look for 'bcast' in the reach column or 'BCST' in the flags column, indicating active broadcast communication.
    Affected if The system has an active broadcast association receiving time from a broadcast server.

You are affected if NTP version is below 4.2.8p6 (or between 4.3.0 and 4.3.90) AND the system is configured to receive NTP broadcasts (broadcastclient mode).

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
Upgrade available Upgrade to 4.2.8 / 4.3.90 / 10.1 or later
Fixed in 4.2.84.3.9010.1
Interim mitigation

Upgrade NTP to version 4.2.8p6 or later (or 4.3.90+ for the 4.3.x branch). If upgrade is not feasible, disable NTP broadcast mode or implement authenticated broadcast mode to prevent unauthorized packet injection.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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Scan for this in your stack

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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-2015-7973 in production — separate from our analysis above.

No notes yet

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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