Date: Mon, 20 Mar 2023 08:26:06 +0100 (CET) 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: CVE-2023-27534: SFTP path ~ resolving discrepancy CVE-2023-27534: SFTP path ~ resolving discrepancy ================================================= Project curl Security Advisory, March 20th 2023 - [Permalink](https://curl.se/docs/CVE-2023-27534.html) VULNERABILITY ------------- curl supports SFTP transfers. curl's SFTP implementation offers a special feature in the path component of URLs: a tilde (`~`) character as the first path element in the path to denotes a path relative to the user's home directory. This is supported because of wording in the [once proposed to-become RFC draft](https://datatracker.ietf.org/doc/html/draft-ietf-secsh-scp-sftp-ssh-uri-04) that was to dictate how SFTP URLs work. Due to a bug, the handling of the tilde in SFTP path did however not only replace it when it is used stand-alone as the first path element but also wrongly when used as a mere prefix in the first element. Using a path like `/~2/foo` when accessing a server using the user `dan` (with home directory `/home/dan`) would then quite surprisingly access the file `/home/dan2/foo`. This can be taken advantage of to circumvent filtering or worse. We are not aware of any exploit of this flaw. INFO ---- CVE-2023-27534 was introduced in [commit ba6f20a244](https://github.com/curl/curl/commit/ba6f20a244), shipped in curl 7.18.0. CWE-22: Improper Limitation of a Pathname to a Restricted Directory Severity: Low AFFECTED VERSIONS ----------------- - Affected versions: curl 7.18.0 to and including 7.88.1 - Not affected versions: curl < 7.18.0 and curl >= 8.0.0 libcurl is used by many applications, but not always advertised as such! THE SOLUTION ------------ A [fix for CVE-2023-27534](https://github.com/curl/curl/commit/4e2b52b5f7a3bf50a) RECOMMENDATIONS -------------- A - Upgrade curl to version 8.0.0 B - Apply the patch to your local version C - Avoid using tilde in SFTP URL paths. TIMELINE -------- This issue was reported to the curl project on March 5, 2023. We contacted distros@...nwall on March 13, 2023. curl 8.0.0 was released on March 20 2023, coordinated with the publication of this advisory. CREDITS ------- - Reported-by: Harry Sintonen - 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
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.