[SECURITY ADVISORY] curl - use-after-free in handle close

[Daniel Stenberg]

use-after-free in handle close
==============================

Project curl Security Advisory, October 31st 2018 -
[Permalink](https://curl.haxx.se/docs/CVE-2018-16840.html)

VULNERABILITY
-------------

libcurl contains a heap use-after-free flaw in code related to closing an easy
handle.

When closing and cleaning up an "easy" handle in the `Curl_close()` function,
the library code first frees a struct (without nulling the pointer) and might
then subsequently erroneously write to a struct field within that already
freed struct.

We are not aware of any exploit of this flaw.

INFO
----

This bug was introduced in [commit
b46cfbc068](https://github.com/curl/curl/commit/b46cfbc068), February 2018.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2018-16840 to this issue.

CWE-416: Use After Free

Severity: 2.3 (Low)

AFFECTED VERSIONS
-----------------

- Affected versions: libcurl 7.59.0 to and including 7.61.1
- Not affected versions: libcurl < 7.59.0 and >= 7.62.0

curl is used by many applications, but not always advertised as such.

THE SOLUTION
------------

A [patch for
CVE-2018-16840](https://github.com/curl/curl/commit/81d135d67155c5295b1033679c606165d4e28f3f)
is available.

RECOMMENDATIONS
---------------

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

A - Upgrade curl to version 7.62.0

B - Apply the patch to your version and rebuild

TIME LINE
---------

It was reported to the curl project on October 14, 2018. We contacted
***@openwall on October 22.

curl 7.62.0 was released on October 31 2018, coordinated with the publication
of this advisory.

CREDITS
-------

Reported by Brian Carpenter, Geeknik Labs. Patch by Daniel Stenberg.

Thanks a lot!