BSD libc contains a buffer overflow vulnerability in link_ntoa()

Overview

The BSD libc library’s link_ntoa() function may be vulnerable to a classic buffer overflow. It is currently unclear if this issue is exploitable.

Description

CWE-120**: Buffer Copy without Checking Size of Input (‘Classic Buffer Overflow’) -**CVE-2016-6559

Improper bounds checking of the obuf variable in the link_ntoa() function in linkaddr.c 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.

The CVSS score below reflects a worst-case scenario in which an attacker may execute arbitrary code with root permissions. It is unclear if any program exists that would allow exploit in any manner.

---

Impact

The full impact and severity depends on the method of exploit and how the library is used by applications. An attacker may be able to execute arbitrary code, but CERT/CC is currently unaware of a proof of concept.

---

Solution

Apply an update

FreeBSD libc was updated to address this vulnerability. Affected users are encouraged to upgrade to the latest version of libc and/or the latest release of your operating system.

In FreeBSD, the following patch levels (or later) contain a fix:

9.3-RELEASE-p51 10.1-RELEASE-p43 10.2-RELEASE-p26 10.3-RELEASE-p13 11.0-RELEASE-p4

---

Vendor Information

548487

Filter by status: All Affected Not Affected Unknown

Filter by content: __ Additional information available

__ Sort by: Status Alphabetical

Expand all

Javascript is disabled. Click here to view vendors.

Apple Affected

Notified: October 10, 2016 Updated: November 16, 2016

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

FreeBSD Project __ Affected

Notified: October 21, 2016 Updated: November 21, 2016

Statement Date: November 21, 2016

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

In FreeBSD, the following patch levels (or later) contain a fix:

9.3-RELEASE-p51 10.1-RELEASE-p43 10.2-RELEASE-p26 10.3-RELEASE-p13 11.0-RELEASE-p4

HardenedBSD __ Affected

Notified: October 26, 2016 Updated: December 07, 2016

Statement Date: December 07, 2016

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

HardenedBSD has fixed this issue in the latest releases. Please see the commit URLs below.

Vendor References

• <https://github.com/HardenedBSD/hardenedBSD-stable/releases/tag/HardenedBSD-10-STABLE-v46.20&gt;
• <https://github.com/HardenedBSD/hardenedBSD-stable/releases/tag/HardenedBSD-11-STABLE-v46.11&gt;

NetBSD __ Affected

Notified: October 26, 2016 Updated: December 08, 2016

Statement Date: December 08, 2016

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

NetBSD has updated on 20161207 to address this issue.

DesktopBSD Unknown

Notified: October 26, 2016 Updated: October 26, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

DragonFly BSD Project Unknown

Notified: October 26, 2016 Updated: October 26, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

F5 Networks, Inc. Unknown

Notified: October 26, 2016 Updated: October 26, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Juniper Networks Unknown

Notified: October 26, 2016 Updated: October 26, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Nokia Unknown

Notified: October 26, 2016 Updated: October 26, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

OpenBSD __ Unknown

Notified: October 26, 2016 Updated: December 08, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

OpenBSD shares the same affected code, see below:

Vendor References

• <http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libc/net/linkaddr.c?sortby=date&gt;

PC-BSD Unknown

Notified: November 16, 2016 Updated: November 16, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

QNX Software Systems Inc. Unknown

Notified: October 26, 2016 Updated: October 26, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

TrueOS Unknown

Notified: November 16, 2016 Updated: November 16, 2016

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

View all 13 vendors __View less vendors __

CVSS Metrics

Group	Score	Vector
Base	9.3	AV:N/AC:M/Au:N/C:C/I:C/A:C
Temporal	6.9	E:U/RL:OF/RC:C
Environmental	1.7	CDP:ND/TD:L/CR:ND/IR:ND/AR:ND

References

• <https://www.freebsd.org/security/advisories/FreeBSD-SA-16:37.libc.asc&gt;
• <https://github.com/freebsd/freebsd/blob/386ddae58459341ec567604707805814a2128a57/lib/libc/net/linkaddr.c#L132&gt;
• <http://www.tedunangst.com/flak/post/who-even-calls-link-ntoa&gt;
• <http://cwe.mitre.org/data/definitions/120.html&gt;

Acknowledgements

Thanks to the reporter who wishes to remain anonymous.

This document was written by Garret Wassermann.

Other Information

CVE IDs:	CVE-2016-6559
Date Public:	2016-12-06 Date First Published: