FasterXML Jackson is a data processing tool built for Java from an American company FasterXML. Jackson-databind is one of its components with data binding. The component can convert Java objects to json objects, as well as converting json to Java objects.
NVD released information about FasterXML Jackson-databind remote code execution vulnerability on March 2, 2020 with CVE number: CVE-2020-9547. The vulnerability is caused by JNDI injection, which leads to remote code execution. Jackson-databind version 2.0.0 - 18.104.22.168 lack the com.ibatis.sqlmap.engine.transaction.jta.JtaTransactionConfig blacklist. Attackers can exploit this vulnerability to bypass restrictions, perform JNDI injection, then execute arbitrary code on the infected host eventually.
Taking Jackson-databind 2.10.1+ ibatis-sqlmap-22.214.171.1246 as the vulnerability environment for analysis, Jackson-databind will perform internal initialization. Afterwards, the incoming json data will be processed. The vulnerability mainly exists in the com.ibatis.sqlmap.engine.transaction.jta.JtaTransactionConfig class in the ibatis-sqlmap library . Let us track the process of exploiting the vulnerability. After Jackson-databind receives a piece of json data, it will parse the data in the ReaderBasedJsonParser class and the characters bit by bit. The details are as shown below:
We use double quotes to determine the start and end of the field name. The class obtained by parsing the json data will be instantiated in the call method.
We obtain the field names in the incoming json data, and assign values to internal attributes through deserialization.
Then we call methods in the class through reflection.
When the lookup method in the com.ibatis.sqlmap.engine.transaction.jta.JtaTransactionConfig
class is executed, the victim host will access the malicious link passed by the attacker and load a malicious file, thereby triggering a remote code execution attack. As shown
We set up Jackson-databind 2.10.1+ ibatis-sqlmap-126.96.36.1996 environment, pass in specially crafted json data, and let the target server load malicious files on the remote host, thereby executing arbitrary code on the target host. as shown in figure:
Jackson-databind 2.0.0 - 188.8.131.52
March 2, 2020 Sangfor security team detected FasterXML Jackson-databind remote code execution vulnerability CVE-2020-9547.
March 4, 2020 Sangfor FarSight Labs reproduced this vulnerability successfully, then released alerts and solutions.
The official has fixed this vulnerability. Please visit the following link to download the latest version:
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