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Integer overflows in `curl_url_set()`

Project curl Security Advisory, May 22nd 2019 - Permalink

VULNERABILITY

libcurl contains two integer overflows in the curl_url_set() function that if triggered, can lead to a too small buffer allocation and a subsequent heap buffer overflow.

The flaws only exist on 32 bit architectures and require excessive string input lengths.

We are not aware of any exploit of this flaw.

INFO

There are two entry points to this issue, on 32 bit architectures.

By asking libcurl to parse a string, passing in a string longer than 2GB to this API: curl_url_set(uh, CURLUPART_URL, "string", 0); triggers the bug.

Asking libcurl to update a URL with a new string, and URL encoded it in the process, by passing in a string longer than 1.33GB to this API: curl_url_set(uh, CURLUPART_*, "string", CURLU_URLENCODE); triggers the bug.

This bug was introduced in August 2018 in commit fb30ac5a2d.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2019-5435 to this issue.

CWE-131: Incorrect Calculation of Buffer Size

Severity: Low

AFFECTED VERSIONS

Affected versions: libcurl 7.62.0 to and including 7.64.1
Not affected versions: libcurl < 7.62.0 and >= libcurl 7.65.0

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

THE SOLUTION

A fix for CVE-2019-5435 is already merged.

RECOMMENDATIONS

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

A - Upgrade curl to version 7.65.0

B - Apply the patch to your version and rebuild

TIMELINE

The issue was reported to the curl project on April 24, 2019. The patch was communicated to the reporter on April 25, 2019. We contacted distros@openwall on May 15.

curl 7.65.0 was released on May 22 2019, coordinated with the publication of this advisory.

CREDITS

Reported-by: Wenchao Li
Patched-by: Daniel Stenberg

Thanks a lot!

Integer overflows in curl_url_set()