CVE-2016-6559

CVE-2016-6559 is a critical-severity vulnerability in Freebsd with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-119.

Key facts

Description

Improper bounds checking of the obuf variable in the link_ntoa() function in linkaddr.c of the BSD libc library may allow an attacker to read or write from memory. The full impact and severity depends on the method of exploit and how the library is used by applications. According to analysis by FreeBSD developers, it is very unlikely that applications exist that utilize link_ntoa() in an exploitable manner, and the CERT/CC is not aware of any proof of concept. A blog post describes the functionality of link_ntoa() and points out that none of the base utilities use this function in an exploitable manner. For more information, please see FreeBSD Security Advisory SA-16:37.

Frequently asked questions

What is CVE-2016-6559?
Improper bounds checking of the obuf variable in the link_ntoa() function in linkaddr.c of the BSD libc library may allow an attacker to read or write from memory. The full impact and severity depends on the method of exploit and how the library is used by applications. According to analysis by FreeBSD developers, it is very unlikely that applications exist that utilize link_ntoa() in an exploitable manner, and the CERT/CC is not aware of any proof of concept. A blog post describes the functionality of link_ntoa() and points out that none of the base utilities use this function in an exploitable manner. For more information, please see FreeBSD Security Advisory SA-16:37.
How severe is CVE-2016-6559?
CVE-2016-6559 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-2016-6559 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (88th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-6559?
CVE-2016-6559 primarily affects Freebsd. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-6559?
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-2016-6559 published?
CVE-2016-6559 was published on 2018-07-13 and last updated on 2026-06-17.

References

Affected products (5)

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