CVE-2026-54512 in jackson-databind
Summary
by MITRE • 06/24/2026
jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. From 2.10.0 until 2.18.8, 2.21.4, and 3.1.4, jackson-databind's PolymorphicTypeValidator (PTV) is the primary safety mechanism guarding polymorphic deserialization. When polymorphic typing is enabled and a type identifier contains generic parameters (i.e. the type ID string contains when only java.util.ArrayList is allow-listed. The container passes the PTV check; com.evil.Gadget is loaded via Class.forName(name, true, loader), instantiated, and its properties are set from attacker-controlled JSON. This completely bypasses an explicitly configured PTV allow-list. This vulnerability is fixed in 2.18.8, 2.21.4, and 3.1.4.
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Analysis
by VulDB Data Team • 06/24/2026
The jackson-databind library represents a core component in Java applications for handling json data binding and tree-model operations within the Jackson Data Processor ecosystem. This vulnerability specifically targets the PolymorphicTypeValidator (PTV) mechanism that serves as the primary safeguard against dangerous polymorphic deserialization attacks. The flaw exists across multiple version ranges including 2.10.0 through 2.18.8, 2.21.4, and 3.1.4, indicating a persistent issue in the library's security architecture. When developers enable polymorphic typing functionality within jackson-databind, the system relies on PTV to validate type identifiers before allowing deserialization of potentially malicious objects.
The technical mechanism behind this vulnerability involves a specific bypass condition where generic parameters within type identifier strings create a false positive in the validation process. When a type identifier contains generic parameters such as those found in collections or complex object structures, the PTV allows the validation to pass even when only basic types like java.util.ArrayList are explicitly allow-listed. This design flaw creates an opening where attackers can manipulate type identifiers to include malicious class names while maintaining the appearance of legitimate type information. The vulnerability exploits the fact that container types with generic parameters bypass the PTV check, allowing subsequent execution paths to proceed normally.
The operational impact of this vulnerability is severe as it enables remote code execution through carefully crafted json payloads. An attacker can construct a json object containing a type identifier that includes malicious class names within its generic parameter structure. The system passes the PTV validation checks and proceeds to load the specified class using Class.forName(name, true, loader) which executes the class loading process with full permissions. Once loaded, the malicious object is instantiated and populated with properties derived from attacker-controlled json data, effectively allowing arbitrary code execution on the target system. This represents a critical security flaw that can be exploited without authentication, making it particularly dangerous in web applications where user input flows directly into jackson-databind deserialization processes.
This vulnerability aligns with CWE-502 which specifically addresses "Deserialization of Untrusted Data" and maps to attack techniques within the ATT&CK framework under T1203 - Exploitation for Execution. The bypass mechanism demonstrates how security controls can be circumvented through subtle implementation flaws in validation logic, particularly when dealing with complex generic type handling. Organizations using jackson-databind in their applications should immediately upgrade to patched versions 2.18.8, 2.21.4, or 3.1.4 to mitigate this risk. The fix addresses the core validation bypass by strengthening the PTV checks to properly validate generic parameter structures and prevent malicious class loading even when container types appear to pass initial validation. Security teams should also consider implementing additional input sanitization measures and monitoring for unusual deserialization patterns in their applications that utilize this library.