Date: Wed, 11 May 2022 08:38:18 +0200 (CEST) From: Daniel Stenberg <daniel@...x.se> To: curl security announcements -- curl users <curl-users@...ts.haxx.se>, curl-announce@...ts.haxx.se, libcurl hacking <curl-library@...ts.haxx.se>, oss-security@...ts.openwall.com Subject: [SECURITY ADVISORY] curl: percent-encoded path separator in URL host percent-encoded path separator in URL host ========================================== Project curl Security Advisory, May 11 2022 - [Permalink](https://curl.se/docs/CVE-2022-27780.html) VULNERABILITY ------------- 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. INFO ---- This flaw was introduced in [commit 9a8564a920188e](https://github.com/curl/curl/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 ----------------- - 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 SOLUTION ------------ The URL parser now rejects host names that percent-decode into URL separator characters. A [fix for CVE-2022-27780](https://github.com/curl/curl/commit/914aaab9153764e) RECOMMENDATIONS -------------- A - Upgrade curl to version 7.83.1 B - Apply the patch to your local version TIMELINE -------- 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. CREDITS ------- This issue was reported by Axel Chong. Patched by Daniel Stenberg. Thanks a lot! -- / daniel.haxx.se | Commercial curl support up to 24x7 is available! | Private help, bug fixes, support, ports, new features | https://curl.se/support.html
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