Category Archives: Potential Risk of CVE

CVE-2020-11984: About Apache HTTP server 2.4.32 to 2.4.44 mod_proxy_uwsgi (2nd Sep 2020)

Preface: uWSGI is a very active project with a fast release cycle. For this reason the code and the documentation maynot always be in sync.

Background: Currently there are three uwsgi-protocol related apache2 modules available. They are mod_uwsgi,mod_proxy_uwsgi and mod_Ruwsgi. uWSGI is often used for serving Python web applications in conjunction with web servers such as Cherokee and Nginx, which offer direct support for uWSGI’s native uwsgi protocol.

Vulnerability details: By sending a small amount of headers (length close to the LimitRequestFieldSize default value of 8190) through uWSGI open port.RCE against a standard UWSGI config is possible if an attacker can put a controlled name or value into “subprocess_env” that is longer than 0xFFFF bytes.
Remark: If UWSGI is explicitly configured in persistent mode (puwsgi), this can also be used to smuggle a second UWSGI request leading to remote code execution.(In its standard configuration UWSGI only supports a single request per connection, making request smuggling impossible).

Official announcement: https://nvd.nist.gov/vuln/detail/CVE-2020-11984

Remedy: CVE-2020-11984: Fixed an information disclosure bug in mod_proxy_uwsgi (bsc#1175074) – https://lists.opensuse.org/opensuse-security-announce/2020-08/msg00068.html

Heads up! Staying Alert! 1st Sep, 2020.

Preface: IP multicast is commonly used today to deliver stock quotes from stock exchanges to financial service providers and then to the stock analysts or brokerages.

Background: The multicast addresses are in the range 224.0.0.0 through 239.255.255.255. Multicast traffic is blocked in the Layer-3 mode by default or by blocking PIM and IGMP under the security rule. The most important multicast routing protocol for the Internet today is PIM sparse mode, defined in RFC 2362.

Vulnerability details:Cisco Releases Security Advisory for DVMRP Vulnerability in IOS XR Software. This design weakness due to insufficient queue management for IGMP packets. As a result attacker could exploit this vulnerability by sending craft IGMP traffic to the vulnerable device. A successful exploit could allow the attacker to cause memory exhaustion, resulting in instability of other processes. These processes may include, but are not limited to, interior and exterior routing protocols. Perhaps the drawings can provide an overview for reference.

Official announcement: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dvmrp-memexh-dSmpdvfz

Remark: IOS XR is a train of Cisco Systems’ widely deployed Internetworking Operating System (IOS), used on their high-end Network Converging System (NCS), carrier-grade routers such as the CRS series, 12000 series, and ASR9000 series.

Maybe this is a outdated news, but Zoom users should pay attention – CVE-2020-9767 (31st Aug 2020)

Preface: Geometric progression up growth in net meeting software product recently because of COVID-19 effect.

Background: We are all concerning of privileges escalation vulnerability. Recap OS vulnerability in past impact Zoom product. The GHOST vulnerability trigger “buffer overflow” bug that affects the gethostbyname () and gethostbyname2 () function calls in the glibc library. The vulnerability could allow remote attackers who could execute arbitrary code with the privileges of the user running the application to invoke any of these functions.

Which components of Zoom may be affected?
You have installed a meeting connector, virtual room connector, or phone connector / gateway that is running.
CentOS Linux versions 5.x, 6.x and 7.x

Remedy: yum update glibc

Recently News: In June 10, 2020 (about 4 months ago). Found that Zoom Sharing Service (Cptservice[.]exe) contains insufficient signature checks of dynamic loaded DLLs and EXEs when loading a signed executable. Such design weakness allow an attacker who had local access to a machine on which the service was running with elevated privileges to elevate their system privileges as well through use of a malicious DLL. NVD Published this vulnerability on 14th Aug 2020. Perhaps quite a lot of users already received alert. For those who do not know. You should upgrade the software immediately.

Remedy: https://support.zoom.us/hc/en-us/articles/360044350792-Security-CVE-2020-9767

Security focus – Fileless malware execution with powershell (27-08-2020)

Preface: Modern Cyber Defense solution without difficulties detect malicious activities. For instance, applications need approved permissions before installation; and security software can scan files to be written, read, and/or executed to check for known signatures. But we still heard data breach incident occurred. Why?

Detail description: On 26th Aug, 2020, US Homeland security published articles to urge public that at least three different types of malware on the way to approaching banking finance, business and computer end user. By this chance, we are going to focus a malware named “BeagleBoyhz”. The BeagleBoyz use a variety of techniques to run their code on local and remote victim systems. Quite a lot of cyber security services vendor observe that Fileless Malware Execution with PowerShell Is Easier to evade antivirus and firewall. In order to avoid their activities detected by defense mechanism. Attacker will abuse Command and Scripting Interpreter technique to executing arbitrary commands.Meanwhile, this is the security focus highlighted by the Department of Homeland Security. As a large number of articles describe different types of malware. If you want to read the details, please refer to the website link.

https://us-cert.cisa.gov/ncas/alerts/aa20-239a

https://us-cert.cisa.gov/northkorea

Remedy: If your current cyber defense solution capable to support regular expression filter function. You can create generic policies to deny the unknown PowerShell script. For example:

.\bi[“’]*e[“’]x\b.*
blocks Invoke-Expression.
At the end, I would like to thanks for McAfee providing this effective solution.

Learn about ATM technology through NCR vulnerabilities (26th Aug 2020)

Preface: A few years ago, ATM attackers might have the opportunity to compromise ATM machines through this method (Raspberry Pi + Python + Wifi). It looks that it is not possible right now.

Study Road Map: From a security perspective, the design weaknesses disclosed by the vendor this time are divided by 3 types.
– Insufficient encryption strength (CVE-2020-10125),
– Main weaknesses in authentication bypass (CVE-2020-10126)
– Lack of data protection (CVE-2020-10124)

Before reading the details of the vulnerability note (VU#815655). We should know the main product specifications.
1. What is XFS?
eXtensions for Financial Services, or XFS, is an open systems middleware international standard promoted by the European Committee for Standardization (CEN) that allows software from multiple vendors to run on different manufacturers’ATMs and other types of payment terminals.

2. What is BNA?
BNA (Bunched Note Acceptor) – Depository that accepts many varied notes without an envelope.

3. Read the vulnerability description (see URL below). Increase your imagination through attached diagram. Maybe you will dig more details, not just the official announcement.

https://kb.cert.org/vuls/id/815655

4. Take your time.

CVE-2020-7711- Pure Go repositories (goxmidsig) vulnerability – 23-08-2020

Preface: SAML 2.0 implementation for Service Providers based on etree and goxmldsig, a pure Go implementation of XML digital signatures.

Background: “nil” in Go that represents zero values for pointers, interfaces, channels, maps, slices and function types.

Vulnerability Details: A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Reference: When “Go” initializes the pointer, it assigns the value of pointer i to nil, but the value of i represents the address of *i. If nil, the system has not assigned an address to *i. So at this time, * i assignment will have problem occur.

Remedy: Official announcement not announce yet. See whether it can apply the similar syntax to do a short term remediation of this design weakness? The gosmal2 package has encountered the similar technical matter (nil point dereference) on Aug 14, 2019 . For more details, please refer to diagram.

CVE-2020-8620 can be transformed as a tool to bother DNS sinkhole function – 23 Aug 2020

Preface: BIND (Berkeley Internet Name Domain) is the most commonly used DNS software on the Internet today. DNS servers that use BIND as server software account for about 90% of all DNS servers.

Technical background: The BIND nameserver is based on a custom event queueing system that wraps around the libuv library (http://libuv.org) for performing asynchronous I/O as needed by the server. libuv is a multi-platform support library with a focus on asynchronous I/O. It was primarily developed for use by Node.js, but it’s also used by Luvit, Julia, pyuv, and others.

Remark: A DNS zone transfer is a procedure that lets two DNS servers exchange their zones. This is needed for redundancy. There are several zone transfer methods but the most common one uses the AXFR protocol.

Vulnerability details: When handling TCP traffic through the libuv library. Due to a length specified within a callback for the library (lib/isc/netmgr/tcpdns.c), flooding the server TCP port used for larger DNS requests (AXFR) will cause the libuv library to pass the length to the server. Therefore, it will result in a violation of the assertion check in the server verification. This assertion check will terminate the service, resulting in a denial of service condition. An attacker can flood ports with unauthenticated packets to trigger this vulnerability.

For information on CVE-2020-8620, thanks to Cisco TALOS.

Official announcement: https://kb.isc.org/docs/cve-2020-8620

Do not use insecure deserializer BinaryFormatter – 19th Aug 2020

Preface: SharePoint is a web-based collaborative platform that integrates with Microsoft Office.So called WebParts”gadgets” that provide new functionality when added to a page.

Background: On July 14, 2020, Microsoft released a security update to fix the vulnerabilities found in the .NET Framework, Microsoft SharePoint and Visual Studio. A proof of concept shown that attacker can use tool so called “YSOSERIAL” . This tool can generating payloads that exploit unsafe Java object deserialization. In the sense that when attack make use of tool find the class contains no interface members. From technical point of view, the attacker will use the tool in the first step to find classes that do not contain interface members.The way is to generate a base64 payload of a serialized ObjectStateFormatter gadget chain.As a result, attacker can plug the payload into the following DataSet gadget and trigger remote code execution against the target SharePoint Server.

Example: xxxxxxxxx[.]xxx -g TypeConfuseDelegate -f LosFormatter -c mspaint

Remark: ysoserial is a collection of utilities and property-oriented programming “gadget chains” discovered in common java libraries that can, under the right conditions, exploit Java applications performing unsafe deserialization of objects.

Reference: A specially crafted method sequence needs to be created by the attacker. Each method in the sequence is called a “gadget” and the malicious sequence of method calls is known as a “gadget chain”.

Official announcement: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1147

Apache release security advisory for struts 2 (aug 2020)

Preface: Struts2 OGNL is the expression language. OGNL is tightly coupled in Struts2 and used to store form parameters as java bean variables in ValueStack and to retrieve the values from ValueStack in result pages. ActionForm has the following responsibilities:Perform data security verification to prevent malicious data from entering the application.

Vulnerability details: However, it hit the design weakness this time. It let attacker modify an specify attribute (skillName) in a request such that a raw OGNL expression gets passed to the skillName property without further validation.

Remedy: upgrading to Struts 2.5.22

Official recommendation: Don’t use forced evaluation of an attribute other than value using %{…} or ${…} syntax unless really needed for a valid use-case.

Recommendation (2): It is recommend to install the application firewall to enhance the preventive control. It can reduce opportunity let hacker conduct the OGNL expression injection attacks.

Reference:http://mail-archives.us.apache.org/mod_mbox/www-announce/202008.mbox/%3C66006167-999e-a1e5-4a3a-5f1c75a1e8a2%40apache.org%3E

SAP completes the remediation – Let’s review the flaw – CVE-2020-6286

Preface: Path traversal vulnerability perhaps will be ignore by some people. But this design weakness similar provide a channel to attacker conduct a search. The vulnerability described in SAP security notes 2934135 contains with two different vulnerabilities.

Background: SAP NetWeaver is a software stack for many of SAP SE’s applications.It can be used for custom development and integration with other applications and systems, and is built primarily using the ABAP programming language, but also uses C, C++, and Java. AS Java is part of the SAP NetWeaver Application Platform. It provides the complete infrastructure for deploying and running Java applications.

Vulnerability details:

CVE-2020-6287 – Multiple Vulnerabilities in SAP NetWeaver AS JAVA (LM Configuration Wizard)
– Additional CVE – CVE-2020-6286
– Affected Product – SAP NetWeaver AS JAVA (LM Configuration Wizard); Versions – 7.30, 7.31, 7.40, 7.50

Impact: SAP NetWeaver AS JAVA (LM Configuration Wizard), versions – 7.30, 7.31, 7.40, 7.50, allows an unauthenticated attacker to relies on path traversal vulnerability reach EJB Environment and download zip files. After the attack is successful, it can also create user IDs and administrator roles. If you are interested to learn more. Please refer to the diagram.

Official announcement – https://wiki.scn.sap.com/wiki/pages/viewpage.action?pageId=552603345