What’s Vulnerable › Vulnerabilities

CVE-2015-7855

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 31.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2017-08-07 · updated 2026-06-17
• Weakness: CWE-20

Description

The decodenetnum function in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to cause a denial of service (assertion failure) via a 6 or mode 7 packet containing a long data value.

Affected products

• Debian Linux: 7.0, 8.0, 9.0
• Clustered Data ONTAP: all versions
• NetApp Data ONTAP operating in 7-Mode: all versions
• NetApp Oncommand Balance: all versions
• NetApp Oncommand Performance Manager: all versions
• NetApp OnCommand Unified Manager for 7-Mode (core package): all versions
• NTP: from 4.2.0 before 4.2.8; from 4.3.0 before 4.3.77; 4.2.8, 4.2.8-p1, 4.2.8-p1-beta1, 4.2.8-p1-beta2, 4.2.8-p1-beta3, 4.2.8-p1-beta4 (+11) — fixed in 4.2.8, 4.3.77
• Siemens Tim 4R-Ie Dnp3 Firmware: all versions
• Siemens Tim 4R-Ie Firmware: all versions

How to fix

Upgrade to a fixed version: NTP 4.2.8, 4.3.77. Check the vendor advisory for mitigations.

References

• http://support.ntp.org/bin/view/Main/NtpBug2922
• http://www.debian.org/security/2015/dsa-3388
• http://www.securityfocus.com/bid/77283
• http://www.securitytracker.com/id/1033951
• https://bugzilla.redhat.com/show_bug.cgi?id=1274264
• https://cert-portal.siemens.com/productcert/pdf/ssa-497656.pdf
• 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://us-cert.cisa.gov/ics/advisories/icsa-21-103-11
• https://www.exploit-db.com/exploits/40840/
• http://support.ntp.org/bin/view/Main/NtpBug2922

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