Is CVE-2015-7691 in the CISA KEV catalog?

No. CVE-2015-7691 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2015-7691?

CVE-2015-7691 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2015-7691?

CVE-2015-7691 has an EPSS score of 7.10% (93th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2015-7691?

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-2015-7691

HIGHEPSS 93th pctl

7.5

CVSS v3

NVD

Description

The crypto_xmit 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 (crash) via crafted packets containing particular autokey operations. NOTE: This vulnerability exists due to an incomplete fix for CVE-2014-9750.

CWE-20Improper Input Validation

How to fix

Remediation Available

ntpDebian

Fixed in:1:4.2.8p4+dfsg-1CVE-2015-7691

ntpUbuntu

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

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

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

7.10%probability of exploitation in 30 days

93rdpercentile

High risk: more likely to be exploited than 93% of all known CVEs.

References

Vendor Advisory1

support.ntp.org

Third-Party Advisory9

Related Vulnerabilities

Other CWE-20 (Improper Input Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-21985	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2018-7600	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-3452	High	7.5	100%	KEV	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.