Discussion:
[SECURITY ADVISORY] curl: LDAP NULL pointer dereference
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Daniel Stenberg
2018-03-14 06:55:08 UTC
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LDAP NULL pointer dereference
=============================

Project curl Security Advisory, March 14th 2018 -
[Permalink](https://curl.haxx.se/docs/adv_2018-97a2.html)

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

curl might dereference a near-NULL address when getting an LDAP URL.

The function `ldap_get_attribute_ber()` is called to get attributes, but it
turns out that it can return `LDAP_SUCCESS` and still return a `NULL` pointer
in the result pointer when getting a particularly crafted response. This was a
surprise to us and to the code.

libcurl-using applications that allow LDAP URLs, or that allow redirects to
LDAP URLs could be made to crash by a malicious server.

We are not aware of any exploit of this flaw.

INFO
----

The bug is only present in curl versions built to use OpenLDAP.

This bug was introduced in May 2010 in [this
commit](https://github.com/curl/curl/commit/2e056353b00d09).

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2018-1000121 to this issue.

CWE-476: NULL Pointer Dereference

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

- Affected versions: curl 7.21.0 to and including curl 7.58.0
- Not affected versions: curl < 7.21.0 and curl >= 7.59.0

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

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

In curl version 7.59.0, curl checks the pointer properly before using it.

A [patch for CVE-2018-1000121](https://curl.haxx.se/CVE-2018-1000121.patch) is available.

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

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

A - Upgrade curl to version 7.59.0

B - Apply the patch to your version and rebuild

C - Make sure you disable LDAP in your transfers

TIME LINE
---------

It was reported to the curl project on March 6, 2018

We contacted ***@openwall on March 7, 2018.

curl 7.59.0 was released on March 14 2018, coordinated with the publication of
this advisory.

CREDITS
-------

Reported by Dario Weisser. Patch by Daniel Stenberg.

Thanks a lot!
--
/ daniel.haxx.se
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