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Date: Wed, 6 Feb 2019 08:12:37 +0100 (CET)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,,
        libcurl hacking <>,
Subject: [SECURITY ADVISORY] curl: SMTP end-of-response out-of-bounds read

SMTP end-of-response out-of-bounds read

Project curl Security Advisory, February 6th 2019 -


libcurl contains a heap out-of-bounds read in the code handling the
end-of-response for SMTP.

If the buffer passed to `smtp_endofresp()` isn't NUL terminated and contains
no character ending the parsed number, and `len` is set to 5, then the
`strtol()` call reads beyond the allocated buffer. The read contents will not
be returned to the caller.

We are not aware of any exploit of this flaw.


This bug was introduced in October 2013 in
[commit 2766262a68](

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2019-3823 to this issue.

CWE-125: Out-of-bounds Read

Severity: 3.7 (Low)


- Affected versions: libcurl 7.34.0 to and including 7.63.0
- Not affected versions: libcurl < 7.34.0

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


A [patch for CVE-2019-3823]( is available.


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

  A - Upgrade curl to version 7.64.0

  B - Apply the patch to your version and rebuild

  C - Turn off SMTP


The issue was reported to the curl project on January 18, 2019. A patch was
communicated to the reporter on January 19, 2019. We contacted distros@...nwall
on January 28.

curl 7.64.0 was released on February 6 2019, coordinated with the publication
of this advisory.


Reported by Brian Carpenter, Geeknik Labs. Patch by Daniel Gustafsson

Thanks a lot!



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