CVE-2015-7853

CVE-2015-7853 is a critical-severity vulnerability in Ntp with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 12% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-120.

Key facts

• Severity: Critical (CVSS 3.x base score 9.8)
• CVSS v2: 7.5
• EPSS exploit prediction: 12% (96th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-120
• Affected product: Ntp
• Published: 2017-08-07
• Last modified: 2026-06-17

Description

The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to execute arbitrary code or cause a denial of service (crash) via a negative input value.

Frequently asked questions

What is CVE-2015-7853?

The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to execute arbitrary code or cause a denial of service (crash) via a negative input value.

How severe is CVE-2015-7853?

CVE-2015-7853 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2015-7853 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 12% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2015-7853?

CVE-2015-7853 primarily affects Ntp. In total, 23 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2015-7853?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2015-7853 published?

CVE-2015-7853 was published on 2017-08-07 and last updated on 2026-06-17.

References

• http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00020.html
• http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00048.html
• http://lists.opensuse.org/opensuse-security-announce/2016-07/msg00026.html
• http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00042.html
• http://lists.opensuse.org/opensuse-updates/2015-11/msg00093.html
• http://lists.opensuse.org/opensuse-updates/2016-05/msg00114.html
• http://packetstormsecurity.com/files/134082/FreeBSD-Security-Advisory-ntp-Authentication-Bypass.html
• http://packetstormsecurity.com/files/134137/Slackware-Security-Advisory-ntp-Updates.html
• http://support.ntp.org/bin/view/Main/NtpBug2920
• http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151021-ntp
• http://www.securityfocus.com/archive/1/536737/100/0/threaded
• http://www.securityfocus.com/archive/1/536760/100/0/threaded
• http://www.securityfocus.com/archive/1/536796/100/0/threaded
• http://www.securityfocus.com/archive/1/536833/100/0/threaded
• http://www.securityfocus.com/archive/1/archive/1/536737/100/100/threaded
• http://www.securityfocus.com/archive/1/archive/1/536760/100/100/threaded
• http://www.securityfocus.com/archive/1/archive/1/536796/100/100/threaded
• http://www.securityfocus.com/archive/1/archive/1/536833/100/100/threaded
• http://www.securityfocus.com/bid/77273
• http://www.securitytracker.com/id/1033951
• http://www.talosintel.com/vulnerability-reports/
• http://www.ubuntu.com/usn/USN-2783-1
• https://bto.bluecoat.com/security-advisory/sa103
• https://bugzilla.redhat.com/show_bug.cgi?id=1274262
• https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf
• https://security.gentoo.org/glsa/201607-15
• https://security.netapp.com/advisory/ntap-20171004-0001/
• https://us-cert.cisa.gov/ics/advisories/icsa-21-159-11

Affected products (23)

• cpe:2.3:a:ntp:ntp:*:*:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:-:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-beta1:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-beta2:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-beta3:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-beta4:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-beta5:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-rc1:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p1-rc2:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p2:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p2-rc1:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p2-rc2:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p2-rc3:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p3:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p3-rc1:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p3-rc2:*:*:*:*:*:*
• cpe:2.3:a:ntp:ntp:4.2.8:p3-rc3:*:*:*:*:*:*
• cpe:2.3:a:netapp:oncommand_balance:-:*:*:*:*:*:*:*
• cpe:2.3:a:netapp:oncommand_performance_manager:-:*:*:*:*:*:*:*
• cpe:2.3:a:netapp:oncommand_unified_manager:-:*:*:*:*:clustered_data_ontap:*:*
• cpe:2.3:o:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*
• cpe:2.3:o:netapp:data_ontap:-:*:*:*:*:7-mode:*:*

More vulnerabilities in Ntp

• CVE-2018-12327 — Critical (CVSS 9.8): Stack-based buffer overflow in ntpq and ntpdc of NTP version 4.2.8p11 allows an attacker to achieve code execution or…
• CVE-2018-7183 — Critical (CVSS 9.8): Buffer overflow in the decodearr function in ntpq in ntp 4.2.8p6 through 4.2.8p10 allows remote attackers to execute…
• CVE-2015-7871 — Critical (CVSS 9.8): 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…
• CVE-2015-7705 — Critical (CVSS 9.8): The rate limiting feature in NTP 4.x before 4.2.8p4 and 4.3.x before 4.3.77 allows remote attackers to have unspecified…
• CVE-2015-7854 — High (CVSS 8.8): Buffer overflow in the password management functionality in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows…
• CVE-2015-7849 — High (CVSS 8.8): Use-after-free vulnerability in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote authenticated…

All CVEs affecting Ntp →

Other CWE-120 (Classic Buffer Overflow) vulnerabilities

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• CVE-2026-24810 — Critical (CVSS 10.0): Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in rethinkdb (src/cjson modules).…
• CVE-2026-24800 — Critical (CVSS 10.0): Out-of-bounds Write, Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in tildearrow…
• CVE-2025-9962 — Critical (CVSS 10.0): A buffer overflow vulnerability in Novakon P series allows attackers to gain root permission without prior…
• CVE-2010-10016 — Critical (CVSS 10.0): BS.Player version 2.57 (build 1051) contains a vulnerability in its playlist import functionality. When processing .m3u…

Browse all CWE-120 (Classic Buffer Overflow) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

• 197.248.207.139 (ipv4-addr)
• 135.129.128.247 (ipv4-addr)
• 119.201.59.224 (ipv4-addr)
• 42.200.60.186 (ipv4-addr)
• 223.197.153.135 (ipv4-addr)
• 125.212.244.35 (ipv4-addr)
• 202.29.220.126 (ipv4-addr)
• 93.42.227.251 (ipv4-addr)