Advisory

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 reverse tabnabbing with a 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:

Reverse Tabnabbing Overview — Source: OWASP.org

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 specification

This note has been re-released with updated ‘Support Packages & Patches’ information. Applications based on WebDynpro Java allows an unauthenticated remote attacker to redirect users to a malicious site due to insufficient reverse tabnabbing URL validation.

Solution

The property RemoveOpenerBrowsingContext is by default set as true and this will protect all application against reverse tabnabbing. For unprotecting specific applications the complete URLs (seperated by commas) can be provided in OpenerAllowList.

Affected System

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

Releated advisories

Disclaimer

SecurityBridge takes the security of SAP products very seriously. We very much encourage the responsible disclosure of security vulnerabilities. If you have detected a vulnerability concerning one of the SAP software products – either in the latest or in a former product version follow the guidelines and processes in accordance with the SAP portal page “Report a Security Vulnerability to SAP”.

The advisories found within the SecurityBridge advisory are generated and continuously enriched by our Team at SecurityBridge and affiliated security consultants, partners, customers of the SecurityBridge Platform, SAP support, and advisory groups.

We do not disclose zero-day vulnerabilities unless a security patch has been made available to the public. In such case, the platform only provides details on which version or signature updates are available within the SecurityBridge platform in order to monitor or measure the vulnerability.

In accordance with SAP guidelines, SecurityBridge only discloses issues where the fixing security note has been released. The vulnerability platform makes no references to available exploits or Proof of Concepts (PoC). Advisories and vulnerabilities will always mention the fixing security note or hints to the corresponding SAP documentation.

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Notifications

Affected system Java

CVSS 4.7

Component BC-WD-JAV

Patch Day2021-03

Released on2021/03/09

SAP Note 2976947

Workaround No

Advisory

Risk specification

Solution

Affected System

Disclaimer

_{Affected system}
Java

_CVSS
4.7

_Component
BC-WD-JAV

_{Patch Day}
2021-03

_{Released
on}
2021/03/09

_{SAP Note}
2976947

_Workaround
No