Is CVE-2015-7871 in the CISA KEV catalog?

No. CVE-2015-7871 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2015-7871?

CVE-2015-7871 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2015-7871?

CVE-2015-7871 has an EPSS score of 81.76% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2015-7871?

Upgrade ntp on debian 11 to 1:4.2.8p4+dfsg-1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2015-7871

CRITICALEPSS 100th pctl

9.8

CVSS v3

NVD

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.

CWE-287Improper Authentication

How to fix

Remediation Available

ntpDebian

Fixed in:1:4.2.8p4+dfsg-1CVE-2015-7871

ntpUbuntu

Fixed in:1:4.2.6.p5+dfsg-3ubuntu2.14.04.5USN-2783-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

81.76%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

References

Vendor Advisory1

support.ntp.org

Third-Party Advisory8

Other references1

cert-portal.siemens.com

Related Vulnerabilities

Other CWE-287 (Improper Authentication) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-35082	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2023-35078	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2017-7921	Critical	9.8	100%	KEV	-
CVE-2024-7593	Critical	9.8	100%	KEV	-
CVE-2023-46805	High	8.2	100%	KEV + Ransom	-
CVE-2022-40684	Critical	9.8	100%	KEV + Ransom	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-13.