Insecure Deserialization
Insecure deserialization occurs when an application converts serialized data (a stream of bytes representing an object's state) back into a living object without proper validation.
How It Works
Insecure deserialization occurs when an application converts serialized data (a stream of bytes representing an object's state) back into a living object without proper validation. Serialization frameworks in languages like Java, PHP, Python, and .NET allow objects to be transformed into byte streams for storage or transmission, then reconstructed later. The vulnerability arises because deserialization can trigger code execution through the object's methods during reconstruction.
Attackers exploit this by crafting malicious serialized payloads containing specially chosen objects that chain together through "gadget chains" — sequences of method calls in existing application libraries. When the application deserializes the attacker's payload, it automatically invokes these methods in sequence, ultimately achieving arbitrary code execution. For example, in Java applications, an attacker might create a serialized object that, when deserialized, triggers a chain through Apache Commons Collections classes, ending in runtime command execution.
The attack typically begins with identifying an endpoint that accepts serialized data — often in cookies, API parameters, or message queue payloads. The attacker then uses tools like ysoserial (Java) or phpggc (PHP) to generate weaponized payloads targeting known gadget chains in the application's dependencies. Because deserialization happens automatically and often before any application logic executes, these attacks frequently bypass authentication and input validation.
Impact
- Remote code execution — attackers gain complete control of the server, executing arbitrary system commands
- Authentication bypass — deserializing manipulated user/session objects grants unauthorized access without credentials
- Privilege escalation — modifying serialized role or permission objects to gain administrative access
- Data exfiltration — reading sensitive files or database contents through executed code
- Denial of service — crafting objects that consume excessive memory or CPU during deserialization
Real-World Examples
SolarWinds Web Help Desk suffered two separate deserialization vulnerabilities in rapid succession. CVE-2025-40551 allowed unauthenticated attackers to achieve remote code execution by sending malicious serialized Java objects to the application. Even after patching, researchers discovered a second deserialization flaw in the same product, demonstrating how deeply embedded these vulnerabilities can be in application architectures.
Jenkins automation servers have experienced multiple Java deserialization vulnerabilities where attackers exploited the CLI protocol to send crafted objects, gaining full control over build servers. These attacks were particularly severe because Jenkins instances often have extensive network access and stored credentials for deploying applications.
WordPress and other PHP applications have faced attacks through unserialize() vulnerabilities in plugins, where attackers embedded malicious PHP objects in user-controllable data fields. Successful exploitation enabled attackers to install backdoors by writing arbitrary PHP files to the web root.
Mitigation
- Avoid deserializing untrusted data entirely — redesign systems to use data-only formats like JSON instead of native serialization
- Implement strict allowlists — configure deserialization libraries to only accept explicitly permitted classes, blocking all others
- Apply cryptographic signatures — sign serialized data and validate signatures before deserialization to ensure integrity
- Use isolated environments — deserialize in sandboxed processes with minimal privileges to contain potential exploitation
- Update vulnerable libraries — patch frameworks and remove dependencies with known gadget chains
- Monitor deserialization activity — log and alert on deserialization operations, especially from external sources
Recent CVEs (3171)
Use-after-free vulnerability in the process_nested_data function in ext/standard/var_unserializer.re in PHP before 5.4.36, 5.5.x before 5.5.20, and 5.6.x before 5.6.4 allows remote attackers to. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 88.3%.
luni/src/main/java/java/io/ObjectInputStream.java in the java.io.ObjectInputStream implementation in Android before 5.0.0 does not verify that deserialization will result in an object that met the. Rated high severity (CVSS 7.2), this vulnerability is low attack complexity. Epss exploitation probability 82.2% and no vendor patch available.
Integer overflow in the object_custom function in ext/standard/var_unserializer.c in PHP before 5.4.34, 5.5.x before 5.5.18, and 5.6.x before 5.6.2 allows remote attackers to cause a denial of. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 56.0%.
htdocs_ari/includes/login.php in the ARI Framework module/Asterisk Recording Interface (ARI) in FreePBX before 2.9.0.9, 2.10.x, and 2.11 before 2.11.1.5 allows remote attackers to execute arbitrary. Rated critical severity (CVSS 10.0), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 52.0%.
The News (tt_news) extension before 3.5.2 for TYPO3 allows remote attackers to have unspecified impact via vectors related to an "insecure unserialize" issue. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity.
inc/ticket.class.php in GLPI 0.83.9 and earlier allows remote attackers to unserialize arbitrary PHP objects via the _predefined_fields parameter to front/ticket.form.php. Rated medium severity (CVSS 6.4), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 12.3%.
Unspecified vulnerability in Oracle Java SE 5.0u55, 6u65, and 7u45; Java SE Embedded 7u45; and OpenJDK 7 allows remote attackers to affect integrity via vectors related to JAAS. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
The Content Editing Wizards component in TYPO3 4.5.0 through 4.5.31, 4.7.0 through 4.7.16, 6.0.0 through 6.0.11, and 6.1.0 through 6.1.6 allows remote authenticated backend users to unserialize. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
The com.ibm.rmi.io.SunSerializableFactory class in IBM Java SDK 7.0.0 before SR6 allows remote attackers to bypass a sandbox protection mechanism and execute arbitrary code via vectors related to. Rated critical severity (CVSS 9.3), this vulnerability is remotely exploitable. No vendor patch available.
Unspecified vulnerability in the Apache Solr for TYPO3 (solr) extension before 2.8.3 for TYPO3 has unknown impact and remote attack vectors, related to "Insecure Unserialize.". Rated critical severity (CVSS 10.0), this vulnerability is remotely exploitable, low attack complexity.
The default configuration of the ObjectRepresentation class in Restlet before 2.1.4 deserializes objects from untrusted sources, which allows remote attackers to execute arbitrary Java code via a. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. This Deserialization of Untrusted Data vulnerability could allow attackers to execute arbitrary code through malicious serialized objects.
wp-includes/functions.php in WordPress before 3.6.1 does not properly determine whether data has been serialized, which allows remote attackers to execute arbitrary code by triggering erroneous PHP. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available.
Unspecified vulnerability in the Store Locator (locator) extension before 3.1.5 for TYPO3 has unknown impact and remote attack vectors, related to "Insecure Unserialize.". Rated critical severity (CVSS 10.0), this vulnerability is remotely exploitable, low attack complexity.
ResourceBuilderImpl.java in the RichFaces 3.x through 5.x implementation in Red Hat JBoss Web Framework Kit before 2.3.0, Red Hat JBoss Web Platform through 5.2.0, Red Hat JBoss Enterprise. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 24.1%.
The BrokerFactory functionality in Apache OpenJPA 1.x before 1.2.3 and 2.x before 2.2.2 creates local executable JSP files containing logging trace data produced during deserialization of certain. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 14.6%.
plugins/system/highlight/highlight.php in Joomla!. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
The Cubecart::_basket method in classes/cubecart.class.php in CubeCart 5.0.0 through 5.2.0 allows remote attackers to unserialize arbitrary PHP objects via a crafted shipping parameter, as. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 31.0%.
Unspecified vulnerability in the Java Runtime Environment (JRE) component in Oracle Java SE 7 through Update 11, 6 through Update 38, and 5.0 through Update 38, and OpenJDK 6 and 7, allows remote. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
OpenStack Object Storage (swift) before 1.7.0 uses the loads function in the pickle Python module unsafely when storing and loading metadata in memcached, which allows remote attackers to execute. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Deserialization of Untrusted Data vulnerability could allow attackers to execute arbitrary code through malicious serialized objects.
view_help.php in the backend help system in TYPO3 4.5.x before 4.5.19, 4.6.x before 4.6.12 and 4.7.x before 4.7.4 allows remote authenticated backend users to unserialize arbitrary objects and. Rated medium severity (CVSS 4.6), this vulnerability is remotely exploitable. This Deserialization of Untrusted Data vulnerability could allow attackers to execute arbitrary code through malicious serialized objects.
The Extbase Framework in TYPO3 4.6.x through 4.6.6, 4.7, and 6.0 unserializes untrusted data, which allows remote attackers to unserialize arbitrary objects and possibly execute arbitrary code via. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity.
Quick Facts
- Typical Severity
- CRITICAL
- Category
- web
- Total CVEs
- 3171