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Date: Tue, 20 Jun 2017 08:09:39 +0200 (CEST)
From: Daniel Stenberg <>
To: c-ares development <>,
Subject: [SECURITY ADVISORY] c-ares NAPTR parser out of bounds access

c-ares NAPTR parser out of bounds access

Project c-ares Security Advisory, June 20, 2017 -


The c-ares function `ares_parse_naptr_reply()`, which is used for parsing
NAPTR responses, could be triggered to read memory outside of the given input
buffer if the passed in DNS response packet was crafted in a particular way.

We are not aware of any exploits of this flaw.


The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2017-1000381 to this issue.


This flaw exists in the following c-ares versions.

- Affected versions: c-ares 1.8.0 to and including 1.12.0
- Not affected versions: c-ares >= 1.13.0


In version 1.13.0, the `RR_len` value gets checked properly and the function
is also added to the fuzz testing. It was previously accidentally left out
from that.

A [patch for CVE-2017-1000381](
is available.


We suggest you take one of the following actions immediately, in order of

  A - Upgrade c-ares to version 1.13.0

  B - Apply the patch to your version and rebuild

  C - Do not use `ares_parse_naptr_reply()`.


It was reported to the c-ares project on May 20. We contacted distros@...nall
on June 16.

c-ares 1.13.0 was released on June 20 2017, coordinated with the publication
of this advisory.


Thanks to LCatro for the report and to David Drysdale for the fix.



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