One year after researchers saw the first attempts to exploit a critical remote code execution flaw affecting the Apache Struts 2 framework, hackers continue to scan the Web for vulnerable servers.
The vulnerability in question, tracked as CVE-2017-5638, affects Struts 2.3.5 through 2.3.31 and Struts 2.5 through 2.5.10. The security hole was addressed on March 6, 2017 with the release of versions 2.3.32 and 220.127.116.11.
The bug, caused due to improper handling of the Content-Type header, can be triggered when performing file uploads with the Jakarta Multipart parser, and it allows a remote and unauthenticated attacker to execute arbitrary OS commands on the targeted system.
The first exploitation attempts were spotted one day after the patch was released, shortly after someone made available a proof-of-concept (PoC) exploit. Some of the attacks scanned servers in search of vulnerable Struts installations, while others were set up to deliver malware.
Guy Bruneau, researcher and handler at the SANS Internet Storm Center, reported over the weekend that his honeypot had caught a significant number of attempts to exploit CVE-2017-5638 over the past two weeks.
The expert said his honeypot recorded 57 exploitation attempts on Sunday, on ports 80, 8080 and 443. The attacks, which appear to rely on a publicly available PoC exploit, involved one of two requests designed to check if a system is vulnerable.
Bruneau told SecurityWeek that he has yet to see any payloads. The researcher noticed scans a few times a week starting on March 13, coming from IP addresses in Asia.
“The actors are either looking for unpatched servers or new installations that have not been secured properly,” Bruneau said.
The CVE-2017-5638 vulnerability is significant as it was exploited by cybercriminals last year to hack into the systems of U.S. credit reporting agency Equifax. Attackers had access to Equifax systems for more than two months and they managed to obtain information on over 145 million of the company’s customers.
The same vulnerability was also leveraged late last year in a campaign that involved NSA-linked exploits and cryptocurrency miners.
This is not the only Apache Struts 2 vulnerability exploited by malicious actors since last year. In September, security firms warned that a remote code execution flaw tracked as CVE-2017-9805 had been exploited to deliver malware.