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Date: Wed, 22 May 2019 09:23:51 +0200 (CEST)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,,
        libcurl hacking <>,
Subject: [SECURITY ADVISORY] curl: Integer overflows in curl_url_set

Integer overflows in `curl_url_set()`

Project curl Security Advisory, May 22nd 2019 -


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.


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: 3.7 (Low)


- 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.


A [fix for CVE-2019-5435]( is already merged.


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

  A - Upgrade curl to version 7.65.0

  B - Apply the patch to your version and rebuild


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@...nwall
on May 15.

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


Reported by Wenchao Li. Patch by Daniel Stenberg

Thanks a lot!


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