percent-encoded path separator in URL host
Project curl Security Advisory, May 11 2022 - Permalink
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
http://example.com%2F10.0.0.1/, would be allowed by the parser and get transposed into
http://example.com/10.0.0.1/. This flaw can be used to circumvent filters, checks and more.
We are not aware of any exploit of this flaw.
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2022-27780 to this issue.
CWE-177: Improper Handling of URL Encoding
- 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 characters.
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@openwall 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!