curl / Docs / Security Problems / RTSP bad headers buffer over-read

RTSP bad headers buffer over-read

Project curl Security Advisory, May 16th 2018 - Permalink

VULNERABILITY

curl can be tricked into reading data beyond the end of a heap based buffer used to store downloaded content.

When servers send RTSP responses back to curl, the data starts out with a set of headers. curl parses that data to separate it into a number of headers to deal with those appropriately and to find the end of the headers that signal the start of the "body" part.

The function that splits up the response into headers is called Curl_http_readwrite_headers() and in situations where it can't find a single header in the buffer, it might end up leaving a pointer pointing into the buffer instead of to the start of the buffer which then later on may lead to an out of buffer read when code assumes that pointer points to a full buffer size worth of memory to use.

This could potentially lead to information leakage but most likely a crash/denial of service for applications if a server triggers this flaw.

We are not aware of any exploit of this flaw.

INFO

This bug was originally introduced in May 2003 in this commit but it didn't become a problem until we added RTSP in January 2010 in this commit.

We have only proven this to trigger with RTSP traffic even though this is code shared with HTTP. We believe this is not a problem for HTTP transfers.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2018-1000301 to this issue.

CWE-126: Buffer Over-read

AFFECTED VERSIONS

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

THE SOLUTION

In curl version 7.60.0, curl makes sure to restore the pointer back to where its supposed to point.

A patch for CVE-2018-1000301 is available.

RECOMMENDATIONS

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

A - Upgrade curl to version 7.60.0

B - Apply the patch to your version and rebuild

TIME LINE

It was reported to the curl project on March 24, 2018

We contacted distros@openwall on May 7, 2018.

curl 7.60.0 was released on May 16 2018, coordinated with the publication of this advisory.

CREDITS

Detected by OSS-fuzz. Assisted by Max Dymond. Patch by Daniel Stenberg.

Thanks a lot!