Glibc Gets Patched For Three Year Old Security Vulnerability

Written by Michael Larabel in GNU on 21 January 2019 at 06:08 PM EST. 7 Comments
CVE-2016-10739 has been around since April 2016 as implied by the number and finally today this security issue has been fixed in the Git development code for the upcoming Glibc 2.29 GNU C Library.

The CVE-2016-10739 vulnerability is that getaddrinfo() parses IPv4 addresses followed by whitespace and any arbitrary characters. With allowing applications to think a string is a valid IP address when in fact there can be additional text, including new lines -- particularly if it was rogue HTTP header strings appended to that IP or other dangerous text -- it could end up being used for say connecting to say a malicious server.

By itself the vulnerability isn't too dangerous unless exploited with an application calling that function and not carrying out any additional checks. This Red Hat bug report details how this flaw could be paired with Python's httplib to cause an HTTP connection to a malicious server.

This issue is further outlined via this SourceWare bug tracker.

As of this evening, the CVE is addressed by this commit for the upcoming Glibc 2.29 release.
The IPv4 address parser in the getaddrinfo function is changed so that it does not ignore trailing whitespace and all characters after it. For backwards compatibility, the getaddrinfo function still recognizes legacy name syntax, such as interpreted as (octal).

This commit does not change the behavior of inet_addr and inet_aton. gethostbyname already had additional sanity checks (but is switched over to the new __inet_aton_exact function for completeness as well).
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