On 09.02.2021 a security relevant correction has been released by SAP SE. The manufacturer resolves an issue within ABAP.
SAP Note 2974582 addresses "[CVE-2021-21478] Reverse Tabnabbing vulnerability in SAP NetWeaver Application Server ABAP (Applications based on Web Dynpro ABAP)" to prevent reverse tabnabbing with a medium risk for exploitation.
A workaround does not exist, according to SAP Security Advisory team. It is advisable to implement the correction as monthly patch process, the team suggests.
Missing authority checks are still the most common security defect related to authorizations in custom code.
Since SAP uses an explicit authorization model, an authority checks must be coded in order to be executed. If an
explicit check is not coded, all users have access.
This type of vulnerability not only exists in SAP standard it also exists in customer coding. Check your custom
developments for vulnerabilities that pose a risk to your systems. SecurityBridge helps
vulnerabilities before they are implemented in production.
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 specificationSAP Web Dynpro ABAP allows an unauthenticated remote attacker to redirect users to a malicious site due to insufficient reverse tabnabbing URL validation.
A default out-of-the-box protection is applied for all Business Server Pages applications.
The advisory 2974582 describes a problem within an ABAP based systems of a specific version. Affected versions are described below. ABAP software is deployed in various software components and is widely used within the SAP product portfolio.
SAP NetWeaver Application Server (formally known as SAP Web Application Server) is a building block of SAP NetWeaver. It is the foundation for most software products developed by SAP SE. SAP NetWeaver systems exist with Java and/or ABAP stacks. The advisory could be relevant for single and dual-stack ABAP installations.
The advisory is valid for
- SAP_BASIS 700-702 14
- SAP_BASIS 731 19
- SAP_BASIS 804 2
- SAP_UI 750 7
- SAP_UI 752 6
- SAP_UI 753 7
- SAP_UI 754 6
- SAP_UI 755 3
- 4.7 Reverse Tabnabbing vulnerability within SAP NetWeaver Application Server ABAP (Applications based on SAP GUI for HTML)
- 4.7 [CVE-2021-21491] Reverse TabNabbing vulnerability in SAP NetWeaver Application Server Java (Applications based on Web Dynpro Java)
- 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