Category: Breaking

Breaking, Building
by Malte Heinzelmann

DNS exfiltration case study

Lately, we came across a remote code execution in a Tomcat web service by utilizing Expression Language. The vulnerable POST body field expected a number. When sending ${1+2} instead, the web site included a Java error message about a failed conversion to java.lang.Long from java.lang.String with value "3".

From that error message we learned a couple of things:

  • The application uses Java
  • We are able to execute EL expressions
  • Output from the EL engine is always returned as String

Whenever you are able to execute code within a Java Context, the most interesting part is to check whether we can get a Runtime object and execute arbitrary OS commands.

Sending ${Runtime.getRuntime()} resolves to java.lang.Runtime@de30bb. Great, so we can use Runtime.exec(String cmd) to execute arbitrary code? Continue reading “DNS exfiltration case study”

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Breaking
by Nils Emmerich

Jenkins – Groovy Sandbox breakout (SECURITY-1538 / CVE-2019-10393, CVE-2019-10394, CVE-2019-10399, CVE-2019-10400)

Recently, I discovered a sandbox breakout in the Groovy Sandbox used by the Jenkins script-security Plugin in their Pipeline Plugin for build scripts. We responsibly disclosed this vulnerability and in the current version of Jenkins it has been fixed and the according Jenkins Security Advisory 2019-09-12 has been published. In this blogpost I want to report a bit on the technical details of the vulnerability.

Continue reading “Jenkins – Groovy Sandbox breakout (SECURITY-1538 / CVE-2019-10393, CVE-2019-10394, CVE-2019-10399, CVE-2019-10400)”

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Breaking
by Oliver Matula

How to break out of restricted shells with tcpdump

During security assessments we sometimes obtain access to a restricted shell on a target system. To advance further and gain complete control of the system, the next step is usually to break out of this shell. If the restricted shell provides access to certain system binaries, these binaries can often be exploited to perform such a break out. Here we would like to show an interesting example of such a break out by using the tcpdump binary. Continue reading “How to break out of restricted shells with tcpdump”

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Breaking
by Niklaus Schiess

Multiple Vulnerabilities in innovaphone VoIP Products Fixed

Dear all,

innovaphone fixed several vulnerabilities in two VoIP products that we disclosed a while ago. The affected products are the Linux Application Platform and the IPVA. Unfortunately, the release notes are not public (yet?) and the vendor does not include information about the vulnerabilities for the Linux Application Platform. Therefore, we decided to publish some more technical details for the issues. Continue reading “Multiple Vulnerabilities in innovaphone VoIP Products Fixed”

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Breaking
by Benjamin Schwendemann

On the insecurity of math.random and it’s siblings

During code reviews we often see developers using weak RNGs like math.random() to generate cryptographic secrets. We think it is commonly known that weak random number generators (RNG) must not be used for any kind of secret and recommend using secure alternatives. I explicitly did not state a specific language yet, because basically every language offers both weak and strong RNGs.

So I asked myself: What if I use a weak RNG to generate a secret? Is it possible to recover the secret from some derived value, like a hash?

Continue reading “On the insecurity of math.random and it’s siblings”

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Breaking
by Florian Grunow

Plume Twitter Client URL Spoofing

It is possible to spoof the URLs that Plume will open to arbitrary locations because of how Plume parses URLs. The preview of an URL in a tweet will show the complete (at least the host name and the first few chars of the URL) but shortened URL. However, if the URL contains a semicolon (;) the URL that will be opened is the part after the semicolon. Continue reading “Plume Twitter Client URL Spoofing”

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Breaking
by Niklaus Schiess

Pidgin, Word Documents, my Clipboard and I

Lately, I’ve experienced some weird Pidgin crashes when I was copy&pasting into chat windows. The strange part was: I didn’t even know what triggered the crash because I actually didn’t know what was in my clipboard at this exact point. This is a quick write-up of how I investigated the issue and some interesting properties I found out about clipboards.

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