Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [day] [month] [year] [list]
Date: Wed, 11 May 2022 08:38:18 +0200 (CEST)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,, libcurl hacking <>,
Subject: [SECURITY ADVISORY] curl: percent-encoded path separator in URL

percent-encoded path separator in URL host

Project curl Security Advisory, May 11 2022 -


The curl URL parser wrongly accepts percent-encoded URL separators like '/'
when decoding the host name part of a URL, making it a *different* URL using
the wrong host name when it is later retrieved.

For example, a URL like ``, would be allowed by
the parser and get transposed into ``. This flaw
can be used to circumvent filters, checks and more.

We are not aware of any exploit of this flaw.


This flaw was introduced in [commit
9a8564a920188e](, shipped
in curl 7.80.0 when curl added support for percent-encoded host names in URLs.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2022-27780 to this issue.

CWE-177: Improper Handling of URL Encoding

Severity: Medium


- Affected versions: curl 7.80.0 to and including 7.83.0
- Not affected versions: curl < 7.83.0 and curl >= 7.83.1

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


The URL parser now rejects host names that percent-decode into URL separator

A [fix for CVE-2022-27780](


  A - Upgrade curl to version 7.83.1

  B - Apply the patch to your local version


This issue was reported to the curl project on April 28, 2022. We contacted
distros@...nwall on May 5.

libcurl 7.83.1 was released on May 11 2022, coordinated with the publication
of this advisory.


This issue was reported by Axel Chong. Patched by Daniel Stenberg.

Thanks a lot!


  | Commercial curl support up to 24x7 is available!
  | Private help, bug fixes, support, ports, new features

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.