LDAP NULL pointer dereference

Project curl Security Advisory, March 14th 2018 - Permalink

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.

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

CWE-476: NULL Pointer Dereference

Severity: Low

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 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 distros@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
• Patched-by: Daniel Stenberg

Thanks a lot!