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Date: Wed, 21 Jul 2021 09:14:18 +0200 (CEST)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,, libcurl hacking <>,
Subject: [SECURITY ADVISORY] curl: Metalink download sends credentials

Metalink download sends credentials

Project curl Security Advisory, July 21th 2021 -


When curl is instructed to get content using the metalink feature, and a user
name and password are used to download the metalink XML file, those same
credentials are then subsequently passed on to each of the servers from which
curl will download or try to download the contents from. Often contrary to the
user's expectations and intentions and without telling the user it happened.

We are not aware of any exploit of this flaw.


This flaw exists only in the curl tool. libcurl is not affected.

This flaw has existed in curl since commit
[b5fdbe848bc3d]( in curl
7.27.0, released on July 27, 2012.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2021-22923 to this issue.

CWE-522: Insufficiently Protected Credentials

Severity: Medium


- Affected versions: curl 7.27.0 to and including 7.77.0
- Not affected versions: curl < 7.27.0 and curl >= 7.78.0


curl has completely removed the metalink feature as of 7.78.0. No fix for this
flaw will be produced by the curl project.

The fix for earlier versions is to rebuild curl with the metalink support
switched off!


  A - Upgrade curl to version 7.78.0

  B - Make sure you do not use metalink with curl

  C - Disable metalink in your build


This issue was reported to the curl project on May 30, 2021.

This advisory was posted on Jul 21, 2021.


This issue was reported by Harry Sintonen. Patched by Daniel Stenberg.

Thanks a lot!


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