CVE Vulnerabilities

CVE-2020-1927

URL Redirection to Untrusted Site ('Open Redirect')

Published: Apr 02, 2020 | Modified: Nov 07, 2023
CVSS 3.x
6.1
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS 2.x
5.8 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:N
RedHat/V2
RedHat/V3
6.1 MODERATE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Ubuntu
LOW

In Apache HTTP Server 2.4.0 to 2.4.41, redirects configured with mod_rewrite that were intended to be self-referential might be fooled by encoded newlines and redirect instead to an an unexpected URL within the request URL.

Weakness

A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks.

Affected Software

Name Vendor Start Version End Version
Http_server Apache 2.4.0 (including) 2.4.41 (including)
JBoss Core Services Apache HTTP Server 2.4.37 SP2 RedHat httpd *
JBoss Core Services on RHEL 6 RedHat jbcs-httpd24-apr-0:1.6.3-86.jbcs.el6 *
JBoss Core Services on RHEL 6 RedHat jbcs-httpd24-brotli-0:1.0.6-21.jbcs.el6 *
JBoss Core Services on RHEL 6 RedHat jbcs-httpd24-httpd-0:2.4.37-52.jbcs.el6 *
JBoss Core Services on RHEL 6 RedHat jbcs-httpd24-mod_cluster-native-0:1.3.12-41.Final_redhat_2.jbcs.el6 *
JBoss Core Services on RHEL 6 RedHat jbcs-httpd24-mod_http2-0:1.11.3-22.jbcs.el6 *
JBoss Core Services on RHEL 6 RedHat jbcs-httpd24-openssl-1:1.1.1c-16.jbcs.el6 *
JBoss Core Services on RHEL 7 RedHat jbcs-httpd24-apr-0:1.6.3-86.jbcs.el7 *
JBoss Core Services on RHEL 7 RedHat jbcs-httpd24-brotli-0:1.0.6-21.jbcs.el7 *
JBoss Core Services on RHEL 7 RedHat jbcs-httpd24-httpd-0:2.4.37-52.jbcs.el7 *
JBoss Core Services on RHEL 7 RedHat jbcs-httpd24-mod_cluster-native-0:1.3.12-41.Final_redhat_2.jbcs.el7 *
JBoss Core Services on RHEL 7 RedHat jbcs-httpd24-mod_http2-0:1.11.3-22.jbcs.el7 *
JBoss Core Services on RHEL 7 RedHat jbcs-httpd24-openssl-1:1.1.1c-16.jbcs.el7 *
Red Hat Enterprise Linux 7 RedHat httpd-0:2.4.6-95.el7 *
Red Hat Enterprise Linux 8 RedHat httpd:2.4-8030020200818000036.30b713e6 *
Red Hat Software Collections for Red Hat Enterprise Linux 6 RedHat httpd24-httpd-0:2.4.34-18.el6 *
Red Hat Software Collections for Red Hat Enterprise Linux 7 RedHat httpd24-httpd-0:2.4.34-18.el7 *
Red Hat Software Collections for Red Hat Enterprise Linux 7 RedHat httpd24-mod_md-1:2.0.8-1.el7 *
Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUS RedHat httpd24-httpd-0:2.4.34-18.el7 *
Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUS RedHat httpd24-mod_md-1:2.0.8-1.el7 *
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUS RedHat httpd24-httpd-0:2.4.34-18.el7 *
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUS RedHat httpd24-mod_md-1:2.0.8-1.el7 *
Apache2 Ubuntu bionic *
Apache2 Ubuntu eoan *
Apache2 Ubuntu esm-infra-legacy/trusty *
Apache2 Ubuntu focal *
Apache2 Ubuntu trusty *
Apache2 Ubuntu trusty/esm *
Apache2 Ubuntu upstream *
Apache2 Ubuntu xenial *

Potential Mitigations

  • Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
  • When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
  • Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Use a list of approved URLs or domains to be used for redirection.
  • When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
  • For example, ID 1 could map to “/login.asp” and ID 2 could map to “http://www.example.com/". Features such as the ESAPI AccessReferenceMap [REF-45] provide this capability.
  • Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
  • Many open redirect problems occur because the programmer assumed that certain inputs could not be modified, such as cookies and hidden form fields.

References