CVE & CISA-KEV Catalog

CVE-2016-9566

HIGHEPSS 91th pctl
7.8
CVSS v3
NVD

Description

base/logging.c in Nagios Core before 4.2.4 allows local users with access to an account in the nagios group to gain root privileges via a symlink attack on the log file. NOTE: this can be leveraged by remote attackers using CVE-2016-9565.

CWE-59Link FollowingCWE-264Permissions, Privileges, and Access Controls

How to fix

Remediation Available
nagios3Ubuntu
Fixed in:3.5.1-1ubuntu1.1USN-3253-1
Fixed in:3.5.1.dfsg-2.1ubuntu1.1USN-3253-1
nagios3-cgiUbuntu
Fixed in:3.5.1-1ubuntu1.1USN-3253-1
Fixed in:3.5.1.dfsg-2.1ubuntu1.1USN-3253-1
nagios3-coreUbuntu
Fixed in:3.5.1-1ubuntu1.1USN-3253-1
Fixed in:3.5.1.dfsg-2.1ubuntu1.1USN-3253-1

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 VectorLocal
Attack ComplexityLow
Privileges RequiredLow
User InteractionNone
ScopeUnchanged

Impact

ConfidentialityHigh
IntegrityHigh
AvailabilityHigh

CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

4.88%probability of exploitation in 30 days
91stpercentile

High risk: more likely to be exploited than 91% of all known CVEs.

References

Vendor Advisory1
Third-Party Advisory2
Issue Tracking1

Related Vulnerabilities

Other CWE-59 (Link Following) vulnerabilities, ordered by exploit likelihood. View all

CVESeverityCVSSEPSSExploitedFix
CVE-2022-30333High7.599%KEV + RansomFix
CVE-2021-21300High8.089%-Fix
CVE-2021-32610High7.173%-Fix
CVE-2020-36193High7.571%KEVFix
CVE-2023-40028Medium4.958%-Fix
CVE-2023-36874High7.843%KEVFix

Common questions

How do I fix CVE-2016-9566?

Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2016-9566 being actively exploited?

Not that we know of. CVE-2016-9566 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 4.9% is the estimated probability that it will be exploited in the next 30 days. That is higher than 91% of all scored CVEs.

How severe is CVE-2016-9566?

CVE-2016-9566 has a CVSS v3 base score of 7.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2016-9566 affect?

Published advisories record a fix for nagios3 (Ubuntu), nagios3-cgi (Ubuntu), nagios3-core (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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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 2026-05-06.