If you haven’t yet patched this critical hole in SAP NetWeaver Application Server, today is not your day

We hope you’ve patched CVE-2020-6262, aka note 2835979, that affects SAP NetWeaver Application Server ABAP, because the folks who found and reported the vulnerability are going public with the details.

SEC Consult will today, we’re told, reveal the nitty-gritty of the flaw on its website, giving miscreants the info they need to exploit any vulnerable systems they can find. The infosec biz’s Alexander Meier and Fabian Hag found the security hole and reported it to SAP in April. It was patched in May.

This critical-severity bug – scoring 9.9 out of 10 on the CVSS v3 meter – can be exploited by a rogue authenticated user, or someone whose access has been hijacked, to inject arbitrary code into an application server. This means they can run malicious commands they shouldn’t be able to on the server, download sensitive information, or crash the installation.

It appears exploitation relies on the presence of the remote function module /SDF/GEN_FUNCS_FUNC_CALL in a Netweaver installation; this module is used by SAP’s Solution Manager admin tool to send ABAP commands to the application server. The bug is a classic failure to sanitize this input data, allowing someone with access to Solution Manager to inject ABAP code into the app server via the aforementioned remote function module.

“During investigations, we observed that data from the VALUE field within the table PT_IMPORTING never gets checked for malicious input or is otherwise validated or sanitized,” reads a detailed SEC Consult advisory on the vulnerability, due to be published today and a draft of which was seen by The Register this week.

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“In consequence, an attacker can break out of the desired syntactic instructions. Injecting ABAP code in the VALUE field allows the attacker to manipulate the source code of the generated subroutine pool and thereby the execution logic of the entire module. Since the attacker can freely choose the characters that can be used in this field, arbitrary ABAP code can be injected.

“To exploit this behavior an attacker can supply special characters like ‘ and . to escape the string quotation that is built into the source code. Afterwards, an attacker can simply specify any semantically valid ABAP code that gets executed by the application server.”

The advisory includes proof-of-concept exploits to extract hashed passwords from an SAP system, delete essential system tables, and gain unlimited control over an installation. To avoid mischief or worse on your network, you probably ought to patch this hole.

This is the latest in a series of recently unearthed bugs in Solution Manager, aka SolMan, that can be abused to commandeer SAP systems. Most notably, there was the RECON flaw discovered by the team at Onapsis, which also involved exploiting a lack of input sanitization. ®