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CVE-2015-3145

cookie parser out of boundary memory access

Project curl Security Advisory, April 22 2015 - Permalink

VULNERABILITY

libcurl supports HTTP "cookies" as documented in RFC 6265. Together with each individual cookie there are several different properties, but for this vulnerability we focus on the associated "path" element. It tells information about for which path on a given host the cookie is valid.

The internal libcurl function called sanitize_cookie_path() that cleans up the path element as given to it from a remote site or when read from a file, did not properly validate the input. If given a path that consisted of a single double-quote, libcurl would index a newly allocated memory area with index -1 and assign a zero to it, thus destroying heap memory it was not supposed to.

At best, this gets unnoticed but can also lead to a crash or worse. We have not researched further what kind of malicious actions that potentially this could be used for.

Applications have to explicitly enable cookie parsing in libcurl for this problem to trigger, and if not enabled libcurl does not hit this problem.

INFO

This flaw can also affect the curl command line tool if a similar operation series is made with that.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2015-3145 to this issue.

CWE-124: Buffer Underwrite ('Buffer Underflow')

Severity: Medium

AFFECTED VERSIONS

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

SOLUTION

libcurl 7.42.0 better verifies the input string.

RECOMMENDATIONS

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

A - Upgrade to curl and libcurl 7.42.0

B - Apply the patch and rebuild libcurl

C - Avoid using cookies with libcurl

TIMELINE

It was first reported to the curl project on April 16 2015. We contacted distros@openwall on April 17th.

libcurl 7.42.0 was released on April 22 2015, coordinated with the publication of this advisory.

CREDITS

Thanks a lot!