SAP takes the security of its vast product portfolio very seriously and thus releases security fixes for
vulnerabilities reported by external researchers and their customers every second Tuesday of the month.
SAP Note 2976947
was released on
09.03.2021 and deals with
"[CVE-2021-21491] Reverse TabNabbing vulnerability in SAP NetWeaver Application Server Java (Applications based on Web Dynpro Java)" within Java.
We advice you to follow the instructions, to resolve
medium potential for exploitation
in component BC-WD-JAV.
According to SAP Security Advisory team a workaround does not exist. It is advisable to implement the correction as part of maintenance.
Reverse tabnabbing is an attack where a page linked from the target page is able to rewrite that page, for example
to replace it with a phishing site. The following figure shows a brief illustration:
While the user was originally on the correct page there is a high risk they will not notice that it has been changed to a phishing site.
Risk specificationApplications based on WebDynpro Java allows an unauthenticated remote attacker to redirect users to a malicious site due to insufficient reverse tabnabbing URL validation.
The property RemoveOpenerBrowsingContext is by default set as true and this will protect all applications against reverse tabnabbing. For unprotecting specific applications the complete URLs (separated by commas) can be provided in OpenerAllowList.
SAP Netweaver Application Server Java is part of the SAP NetWeaver Application Platform. It provides the complete infrastructure for deploying and running Java applications.
- The AS Java Home: SAP Netweaver Application Server Java wiki
- A dedicated SAP NetWeaver 7.40 Application Server for Java Security Guide exists.
The advisory is valid for
- SAP_JTECHS 7.00 3
- WD-RUNTIME 7.10-7.11 2
- WD-RUNTIME 7.20 2
- WD-RUNTIME 7.30 2
- WD-RUNTIME 7.31 2
- WD-RUNTIME 7.40 2
- WD-RUNTIME 7.50 2
- 4.7 [CVE-2021-21478] Reverse Tabnabbing vulnerability in SAP NetWeaver Application Server ABAP (Applications based on Web Dynpro ABAP)
- 4.7 Reverse Tabnabbing vulnerability within SAP NetWeaver Application Server ABAP (Applications based on SAP GUI for HTML)
- 4.7 Reverse TabNabbing vulnerability in SAP NetWeaver Application Server Java (Applications based on HTMLB for Java)
- 4.7 Reverse tabnabbing issue in Unified Rendering based frameworks in NetWeaver Application Server Java
- 4.1 Reverse Tabnabbing vulnerability within SAP CRM WebClient UI