--- /dev/null
+Upstream-Status: Backport [ https://subversion.apache.org/security/CVE-2020-17525-advisory.txt ]
+CVE: CVE-2020-17525
+Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com>
+
+ Remote unauthenticated denial-of-service in Subversion mod_authz_svn.
+
+Summary:
+========
+
+ Subversion's mod_authz_svn module will crash if the server is using
+ in-repository authz rules with the AuthzSVNReposRelativeAccessFile
+ option and a client sends a request for a non-existing repository URL.
+
+ This can lead to disruption for users of the service.
+
+Known vulnerable:
+=================
+
+ mod_dav_svn+mod_authz_svn servers 1.9.0 through 1.10.6 (inclusive).
+ mod_dav_svn+mod_authz_svn servers 1.11.0 through 1.14.0 (inclusive).
+
+Known fixed:
+============
+
+ mod_dav_svn+mod_authz_svn servers 1.14.1
+ mod_dav_svn+mod_authz_svn servers 1.10.7
+
+Details:
+========
+
+ A null-pointer-dereference has been found in mod_authz_svn that results in
+ a remote unauthenticated Denial-of-Service in some server configurations.
+
+ The vulnerability can be triggered by an unauthenticated user if the
+ Apache HTTPD server is configured to use an in-repository authz file,
+ with configuration directives such as:
+
+ AuthzSVNAccessFile "^/authz"
+ AuthzSVNReposRelativeAccessFile "^/authz"
+
+ The problem originates when sending a GET request to a non-existent
+ repository. The mod_authz_svn module will attempt to find authz rules
+ at a path within the requested SVN repository. Upon constructing this
+ path, the function svn_repos_find_root_path will return a NULL pointer
+ since the requested repository does not exist on-disk.
+ A check for this legitimate NULL pointer condition is missing, which
+ results in a segmentation fault when the NULL pointer is used.
+
+ The in-repository authz feature was first introduced in Subversion 1.8:
+ https://subversion.apache.org/docs/release-notes/1.8.html#in-repo-authz
+
+ The missing NULL check was first introduced during refactoring of the
+ authz code during development work leading up to Subversion 1.9.
+ Subversion 1.8 servers are unaffected.
+
+Severity:
+=========
+
+ CVSSv3 Base Score: 7.5 (High)
+
+ CVSSv3 Base Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
+
+ Exploitation results in denial of service by crashing the HTTPD worker
+ handling the request. The impact of this differs depending on how the
+ Apache HTTPD server is configured, including the choice of MPM (Multi-
+ Processing-Module). If the worker shares its memory address space with
+ the main thread, as is the case with e.g. the Event MPM, the entire
+ HTTPD server process will terminate. If the pre-fork MPM is used, the
+ worker will terminate but the HTTPD server will stay up, and service
+ availability will depend on how frequently the attacker is able to
+ send malicious requests which target the vulnerability.
+
+Recommendations:
+================
+
+ We recommend all users to upgrade to a known fixed release of the
+ Subversion mod_dav_svn server.
+
+ Users who are unable to upgrade may apply the included patches.
+
+ As a workaround, the use of in-repository authz rules files with
+ the AuthzSVNReposRelativeAccessFile can be avoided by switching
+ to an alternative configuration which fetches an authz rules file
+ from the server's filesystem, rather than from an SVN repository.
+
+References:
+===========
+
+ CVE-2020-17525 (Subversion)
+
+Reported by:
+============
+
+ Thomas Åkesson, simonsoft.se
+
+Patches:
+========
+
+ Patch for Subversion 1.10, 1.14:
+
+[[[
+Index: subversion/libsvn_repos/config_file.c
+===================================================================
+--- a/subversion/libsvn_repos/config_file.c (revision 1883994)
++++ b/subversion/libsvn_repos/config_file.c (working copy)
+@@ -237,6 +237,10 @@ get_repos_config(svn_stream_t **stream,
+ {
+ /* Search for a repository in the full path. */
+ repos_root_dirent = svn_repos_find_root_path(dirent, scratch_pool);
++ if (repos_root_dirent == NULL)
++ return svn_error_trace(handle_missing_file(stream, checksum, access,
++ url, must_exist,
++ svn_node_none));
+
+ /* Attempt to open a repository at repos_root_dirent. */
+ SVN_ERR(svn_repos_open3(&access->repos, repos_root_dirent, NULL,
+]]]
