Advisory

On 09.03.2021 a security relevant correction has been released by SAP SE. The manufacturer resolves an issue within Java.

SAP Note 2977001 addresses "Reverse TabNabbing vulnerability in SAP NetWeaver Application Server Java (Applications based on HTMLB for Java)" 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 part of maintenance, the team suggests.

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

Applications on Web Dynpro Java Server based on SAP HTMLB 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 applications against reverse tabnabbing. For unprotecting specific applications the complete URLs (separated 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

EP-BASIS 7.10-7.11 ⁴
EP-BASIS 7.30 ⁴
EP-BASIS 7.31 ⁴
EP-BASIS 7.40 ⁴
EP-BASIS 7.50 ⁵
FRAMEWORK 7.10-7.11 ⁶
FRAMEWORK-EXT 7.30 ³
FRAMEWORK-EXT 7.31 ³
FRAMEWORK-EXT 7.40 ³
FRAMEWORK-EXT 7.50 ³
LMNWAUIFRMRK 7.10-7.11
LMNWAUIFRMRK 7.30
LMNWAUIFRMRK 7.31
LMNWAUIFRMRK 7.40
LMNWAUIFRMRK 7.50 ²

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 EP-PDK-HBJ

Patch Day2021-03

Released on2021/03/09

SAP Note 2977001

Workaround No

Advisory

Risk specification

Solution

Affected System

Disclaimer

_{Affected system}
Java

_CVSS
4.7

_Component
EP-PDK-HBJ

_{Patch Day}
2021-03

_{Released
on}
2021/03/09

_{SAP Note}
2977001

_Workaround
No